3-Amino-4-phenylbutanoic acid derivatives as dipeptidyl peptidase inhibitors for the treatment or prevention of diabetes

ABSTRACT

The present invention is directed to 3-amino-4-phenylbutanoic acid derivatives which are inhibitors of the dipeptidyl peptidase-IV enzyme (“DP-IV inhibitors”) and which are useful in the treatment or prevention of diseases in which the dipeptidyl peptidase-IV enzyme is involved, such as diabetes and particularly type 2 diabetes. The invention is also directed to pharmaceutical compositions comprising these compounds and the use of these compounds and compositions in the prevention or treatment of such diseases in which the dipeptidyl peptidase-IV enzyme is involved.

BACKGROUND OF THE INVENTION

Diabetes refers to a disease process derived from multiple causativefactors and characterized by elevated levels of plasma glucose orhyperglycemia in the fasting state or after administration of glucoseduring an oral glucose tolerance test. Persistent or uncontrolledhyperglycemia is associated with increased and premature morbidity andmortality. Often abnormal glucose homeostasis is associated bothdirectly and indirectly with alterations of the lipid, lipoprotein andapolipoprotein metabolism and other metabolic and hemodynamic disease.Therefore patients with Type 2 diabetes mellitus are at especiallyincreased risk of macrovascular and microvascular complications,including coronary heart disease, stroke, peripheral vascular disease,hypertension, nephropathy, neuropathy, and retinopathy. Therefore,therapeutical control of glucose homeostasis, lipid metabolism andhypertension are critically important in the clinical management andtreatment of diabetes mellitus.

There are two generally recognized forms of diabetes. In type 1diabetes, or insulin-dependent diabetes mellitus (IDDM), patientsproduce little or no insulin, the hormone which regulates glucoseutilization. In type 2 diabetes, or noninsulin dependent diabetesmellitus (NIDDM), patients often have plasma insulin levels that are thesame or even elevated compared to nondiabetic subjects; however, thesepatients have developed a resistance to the insulin stimulating effecton glucose and lipid metabolism in the main insulin-sensitive tissues,which are muscle, liver and adipose tissues, and the plasma insulinlevels, while elevated, are insufficient to overcome the pronouncedinsulin resistance.

Insulin resistance is not primarily due to a diminished number ofinsulin receptors but to a post-insulin receptor binding defect that isnot yet understood. This resistance to insulin responsiveness results ininsufficient insulin activation of glucose uptake, oxidation and storagein muscle and inadequate insulin repression of lipolysis in adiposetissue and of glucose production and secretion in the liver.

The available treatments for type 2 diabetes, which have not changedsubstantially in many years, have recognized limitations. While physicalexercise and reductions in dietary intake of calories will dramaticallyimprove the diabetic condition, compliance with this treatment is verypoor because of well-entrenched sedentary lifestyles and excess foodconsumption, especially of foods containing high amounts of saturatedfat. Increasing the plasma level of insulin by administration ofsulfonylureas (e.g. tolbutamide and glipizide) or meglitinide, whichstimulate the pancreatic β-cells to secrete more insulin, and/or byinjection of insulin when sulfonylureas or meglitinide becomeineffective, can result in insulin concentrations high enough tostimulate the very insulin-resistant tissues. However, dangerously lowlevels of plasma glucose can result from administration of insulin orinsulin secretagogues (sulfonylureas or meglitinide), and an increasedlevel of insulin resistance due to the even higher plasma insulin levelscan occur. The biguanides increase insulin sensitivity resulting in somecorrection of hyperglycemia. However, the two biguanides, phenformin andmetformin, can induce lactic acidosis and nausea/diarrhea. Metformin hasfewer side effects than phenformin and is often prescribed for thetreatment of Type 2 diabetes.

The glitazones (i.e. 5-benzylthiazolidine-2,4-diones) are a morerecently described class of compounds with potential for amelioratingmany symptoms of type 2 diabetes. These agents substantially increaseinsulin sensitivity in muscle, liver and adipose tissue in severalanimal models of type 2 diabetes resulting in partial or completecorrection of the elevated plasma levels of glucose without occurrenceof hypoglycemia. The glitazones that are currently marketed are agonistsof the peroxisome proliferator activated receptor (PPAR), primarily thePPAR-gamma subtype. PPAR-gamma agonism is generally believed to beresponsible for the improved insulin sensititization that is observedwith the glitazones. Newer PPAR agonists that are being tested fortreatment of Type II diabetes are agonists of the alpha, gamma or deltasubtype, or a combination of these, and in many cases are chemicallydifferent from the glitazones (i.e., they are not thiazolidinediones).Serious side effects (e.g. liver toxicity) have occurred with some ofthe glitazones, such as troglitazone.

Additional methods of treating the disease are still underinvestigation. New biochemical approaches that have been recentlyintroduced or are still under development include treatment withalpha-glucosidase inhibitors (e.g. acarbose) and protein tyrosinephosphatase-1B (PTP-1B) inhibitors.

Compounds that are inhibitors of the dipeptidyl peptidase-IV (“DP-IV” or“DPP-IV”) enzyme are also under investigation as drugs that may beuseful in the treatment of diabetes, and particularly type 2 diabetes.See for example WO 97/40832, WO 98/19998, U.S. Pat. No. 5,939,560,Bioorg. Med. Chem. Lett., 6: 1163-1166 (1996); and Bioorg. Med. Chem.Lett., 6: 2745-2748 (1996). The usefulness of DP-IV inhibitors in thetreatment of type 2 diabetes is based on the fact that DP-IV in vivoreadily inactivates glucagon like peptide-1 (GLP-1) and gastricinhibitory peptide (GIP). GLP-1 and GIP are incretins and are producedwhen food is consumed. The incretins stimulate production of insulin.Inhibition of DP-IV leads to decreased inactivation of the incretins,and this in turn results in increased effectiveness of the incretins instimulating production of insulin by the pancreas. DP-IV inhibitiontherefore results in an increased level of serum insulin.Advantageously, since the incretins are produced by the body only whenfood is consumed, DP-IV inhibition is not expected to increase the levelof insulin at inappropriate times, such as between meals, which can leadto excessively low blood sugar (hypoglycemia). Inhibition of DP-IV istherefore expected to increase insulin without increasing the risk ofhypoglycemia, which is a dangerous side effect associated with the useof insulin secretagogues.

DP-IV inhibitors also have other therapeutic utilities, as discussedherein. DP-IV inhibitors have not been studied extensively to date,especially for utilities other than diabetes. New compounds are neededso that improved DP-IV inhibitors can be found for the treatment ofdiabetes and potentially other diseases and conditions.

SUMMARY OF THE INVENTION

The present invention is directed to 3-amino-4-phenylbutanoic acidderivatives which are inhibitors of the dipeptidyl peptidase-IV enzyme(“DP-IV inhibitors”) and which are useful in the treatment or preventionof diseases in which the dipeptidyl peptidase-IV enzyme is involved,such as diabetes and particularly type 2 diabetes. The invention is alsodirected to pharmaceutical compositions comprising these compounds andthe use of these compounds and compositions in the prevention ortreatment of such diseases in which the dipeptidyl peptidase-IV enzymeis involved.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to 3-amino-4-phenylbutanoic acidderivatives useful as inhibitors of dipeptidyl peptidase-IV. Compoundsof the present invention are described by structural formula I:

or a pharmaceutically acceptable salt thereof; wherein

each n is independently 0, 1, or 2;

X is N or CR²;

Ar is phenyl substituted with one to five R³ substituents;

R¹ and R² are each independently selected from the group consisting of

-   -   hydrogen,    -   halogen,    -   hydroxy,    -   cyano,    -   C₁₋₁₀ alkyl, wherein alkyl is unsubstituted or substituted with        one to five substituents independently selected from halogen or        hydroxy,    -   C₁₋₁₀ alkoxy, wherein alkoxy is unsubstituted or substituted        with one to five substituents independently selected from        halogen or hydroxy,    -   C₁₋₁₀ alkylthio, wherein alkylthio is unsubstituted or        substituted with one to five substituents independently selected        from halogen or hydroxy,    -   C₂₋₁₀ alkenyl, wherein alkenyl is unsubstituted or substituted        with one to five substituents independently selected from        halogen or hydroxy,    -   (CH₂)_(n)COOH,    -   (CH₂)_(n)COOC₁₋₆ alkyl,    -   (CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ are independently selected        from the group consisting of hydrogen, tetrazolyl, thiazolyl,        (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl,        wherein alkyl is unsubstituted or substituted with one to five        halogens and wherein phenyl and cycloalkyl are unsubstituted or        substituted with one to five substituents independently selected        from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein        alkyl and alkoxy are unsubstituted or substituted with one to        five halogens;        -   or R⁴ and R⁵ together with the nitrogen atom to which they            are attached form a heterocyclic ring selected from            azetidine, pyrrolidine, piperidine, piperazine, and            morpholine wherein said heterocyclic ring is unsubstituted            or substituted with one to five substituents independently            selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,            wherein alkyl and alkoxy are unsubstituted or substituted            with one to five halogens;    -   (CH₂)_(n)—NR⁴R⁵,    -   (CH₂)_(n)—OCONR⁴R⁵,    -   (CH₂)_(n)—SO₂NR⁴R⁵,    -   (CH₂)_(n)—SO₂R⁶,    -   (CH₂)_(n)—NR⁷SO₂R⁶,    -   (CH₂)_(n)—NR⁷CONR⁴R⁵,    -   (CH₂)_(n)—NR⁷COR⁷,    -   (CH₂)_(n)—NR⁷CO₂R⁶,    -   (CH₂)_(n)—COR⁶,    -   (CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted        or substituted with one to three substituents independently        selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens,    -   (CH₂)_(n)-aryl, wherein aryl is unsubstituted or substituted        with one to five substituents independently selected from        halogen, cyano, hydroxy, NR⁷SO₂R⁶, SO₂R⁶, CO₂H, C₁₋₆        alkyloxycarbonyl, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and        alkoxy are unsubstituted or substituted with one to five        halogens,    -   (CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or        substituted with one to three substituents independently        selected from hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens, and    -   (CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted or        substituted with one to three substituents independently        selected from oxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆        alkoxy, wherein alkyl and alkoxy are unsubstituted or        substituted with one to five halogens,    -   wherein any methylene (CH₂) carbon atom in R¹ or R² is        unsubstituted or substituted with one to two groups        independently selected from halogen, hydroxy, and C₁₋₄ alkyl        unsubstituted or substituted with one to five halogens;

each R³ is independently selected from the group consisting of

-   -   hydrogen,    -   halogen,    -   cyano,    -   hydroxy,    -   C₁₋₆ alkyl, unsubstituted or substituted with one to five        halogens, and    -   C₁₋₆ alkoxy, unsubstituted or substituted with one to five        halogens;

R⁶ is independently selected from the group consisting of tetrazolyl,thiazolyl, (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl,wherein alkyl is unsubstituted or substituted with one to five halogensand wherein phenyl and cycloalkyl are unsubstituted or substituted withone to five substituents independently selected from halogen, hydroxy,C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstitutedor substituted with one to five halogens, and wherein any methylene(CH₂) carbon atom in R⁶ is unsubstituted or substituted with one to twogroups independently selected from halogen, hydroxy, C₁₋₄ alkyl, andC₁₋₄ alkoxy, wherein alkyl and alkoxy are unsubstituted or substitutedwith one to five halogens;

each R⁷ is hydrogen or R⁶;

R⁸, R⁹ and R¹⁰ are each independently selected from the group consistingof

-   -   hydrogen,    -   cyano,    -   carboxy,    -   C₁₋₆ alkyloxycarbonyl,    -   C₁₋₁₀ alkyl, unsubstituted or substituted with one to five        substituents independently selected from halogen, hydroxy, C₁₋₆        alkoxy; carboxy, C₁₋₆ alkyloxycarbonyl, and phenyl-C₁₋₃ alkoxy,        wherein alkoxy is unsubstituted or substituted with one to five        halogens,    -   (CH₂)_(n)-aryl, wherein aryl is unsubstituted or substituted        with one to five substituents independently selected from        halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and        alkoxy are unsubstituted or substituted with one to five        halogens,    -   (CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or        substituted with one to three substituents independently        selected from hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens,    -   (CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted or        substituted with one to three substituents independently        selected from oxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆        alkoxy, wherein alkyl and alkoxy are unsubstituted or        substituted with one to five halogens,    -   (CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted        or substituted with one to three substituents independently        selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens, and    -   (CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ are independently selected        from the group consisting of hydrogen, tetrazolyl, thiazolyl,        (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl,        wherein alkyl is unsubstituted or substituted with one to five        halogens and wherein phenyl and cycloalkyl are unsubstituted or        substituted with one to five substituents independently selected        from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein        alkyl and alkoxy are unsubstituted or substituted with one to        five halogens;        -   or R⁴ and R⁵ together with the nitrogen atom to which they            are attached form a heterocyclic ring selected from            azetidine, pyrrolidine, piperidine, piperazine, and            morpholine wherein said heterocyclic ring is unsubstituted            or substituted with one to five substituents independently            selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,            wherein alkyl and alkoxy are unsubstituted or substituted            with one to five halogens;    -   wherein any methylene (CH₂) carbon atom in R⁸, R⁹ or R¹⁰ is        unsubstituted or substituted with one to two groups        independently selected from halogen, hydroxy, and C₁₋₄ alkyl        unsubstituted or substituted with one to five halogens;

with the proviso that when X is N, R¹⁰, R¹¹, R¹² and R¹³ are hydrogen,

R⁸ or R⁹ is

-   -   hydrogen;    -   cyano;    -   C₁₋₁₀ alkyl, unsubstituted or substituted with one to five        substituents selected from:        -   (1) halogen,        -   (2) hydroxy,        -   (3) phenyl, optionally substituted with one to five            substituents independently selected from halogen, hydroxy,            C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are            optionally substituted with one to five halogens,        -   (4) naphthyl, optionally substituted with one to five            substituents independently selected from halogen, hydroxy,            C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are            optionally substituted with one to five halogens,        -   (5) CO₂H,        -   (6) CO₂C₁₋₆ alkyl,        -   (7) CONR¹¹R¹², wherein R¹¹ and R¹² are independently            selected from the group consisting of hydrogen, tetrazolyl,            phenyl, C₃₋₆ cycloalkyl and C₁₋₆ alkyl, wherein alkyl is            optionally substituted with one to six substituents            independently selected from halogen and phenyl, wherein the            phenyl or C₃₋₆ cycloalkyl being R¹¹ or R¹² or the optional            phenyl substituent on C₁₋₆ alkyl are optionally substituted            with one to five substituents independently selected from            halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, said C₁₋₆            alkyl and C₁₋₆ alkoxy being optionally substituted with one            to five halogens,        -   or wherein R¹¹ and R¹² are optionally joined to form a ring            selected from pyrrolidine, piperidine and morpholine;    -   phenyl, which is unsubstituted or substituted with one to five        substituents independently selected from C₁₋₆ alkyl, C₁₋₆        alkoxy, hydroxy, and halogen, wherein alkyl and alkoxy are        optionally substituted with one to five halogens;    -   naphthyl, which is unsubstituted or substituted with one to five        substituents independently selected from C₁₋₆ alkyl, C₁₋₆        alkoxy, hydroxy, and halogen, wherein alkyl and alkoxy are        optionally substituted with one to five halogens;    -   CO₂H;    -   C₁₋₆ alkyloxycarbonyl;    -   CONR¹¹R¹²; or    -   C₃₋₆ cycloalkyl, which is optionally substituted with one to        five substituents independently selected from halogen, hydroxy,        C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are        optionally substituted with one to five halogens; and when X is        CR² and

R² is

-   -   hydrogen,    -   cyano,    -   C₁₋₁₀ alkyl, unsubstituted or substituted with one to five        halogens,    -   (CH₂)_(n)-phenyl, which is unsubstituted or substituted with one        to five substituents independently selected from halogen, cyano        hydroxy, R¹³, OR¹³, NHSO₂R¹³, SO₂R¹³, CO₂H, and C₁₋₆        alkyloxycarbonyl, wherein R¹³ is C₁₋₆ alkyl, unsubstituted or        substituted with one to five halogens; or    -   a 5- or 6-membered heterocycle which may be saturated or        unsaturated comprising one to four heteroatoms independently        selected from N, S and O, the heterocycle being unsubstituted or        substituted with one to three substituents independently        selected from oxo, hydroxy, halogen,        -   C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are            optionally substituted with one to five halogens;

then in both cases R¹ is not

-   -   (1) hydrogen,    -   (2) cyano,    -   (3) C₁₋₁₀ alkyl, unsubstituted or substituted with one to five        halogens,    -   (4) (CH₂)_(n)-phenyl, which is unsubstituted or substituted with        one to five substituents independently selected from halogen,        cyano hydroxy, R¹³, OR_(13,) NHSO₂R¹³, SO₂R¹³, CO₂H, and C₁₋₆        alkyloxycarbonyl, wherein R¹³ is C₁₋₆ alkyl, unsubstituted or        substituted with one to five halogens; or    -   (5) a 5- or 6-membered heterocycle which may be saturated or        unsaturated comprising one to four heteroatoms independently        selected from N, S and O, the heterocycle being unsubstituted or        substituted with one to three substituents independently        selected from oxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆        alkoxy, wherein alkyl and alkoxy are optionally substituted with        one to five halogens.

R₁, R¹² and R¹³ are each independently hydrogen or C₁₋₆ alkyl.

In one embodiment of the compounds of the present invention, the carbonatom marked with an * has the R configuration as depicted in formula Ia

wherein Ar, X, R¹, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are as defined herein.

In a second embodiment of the compounds of the present invention, X is Nas depicted in formula Ib:

wherein Ar, R¹, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are as defined herein.

In a class of this second embodiment, the carbon atom marked with an *has the R configuration as depicted in formula Ic:

wherein Ar, R¹, R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are as defined herein.

In another class of this second embodiment of the compounds of thepresent invention, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are hydrogen as depictedin formula Id:

wherein Ar, R¹, and R⁸ are as defined herein.

In a subclass of this class, R⁸ is hydrogen.

In a third embodiment of the compounds of the present invention, X isCR² as depicted in formula Ie:

wherein Ar, R¹, R², R⁸, R⁹, R¹⁰, R₁₁, R¹², and R¹³ are as definedherein.

In a class of this third embodiment, the carbon atom marked with an *has the R configuration as depicted in formula If:

wherein Ar, R¹, R², R⁸, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are as definedherein.

In another class of this third embodiment of the compounds of thepresent invention, R⁹, R¹⁰, R¹¹, R¹², and R¹³ are hydrogen as depictedin formula Ig:

wherein Ar, R¹, R², and R⁸ are as defined herein.

In a subclass of this class, R⁸ is hydrogen.

In a fourth embodiment of the compounds of the present invention, R³ isselected from the group consisting of hydrogen, fluoro, chloro, bromo,trifluoromethyl, and methyl. In a class of this embodiment, R³ isselected from the group consisting of hydrogen, fluoro, and chloro. In asubclass of this class, R³ is hydrogen or fluoro.

In a fifth embodiment of the compounds of the present invention, R¹ isselected from the group consisting of:

-   -   hydrogen,    -   halogen,    -   C₁₋₆ alkyl, wherein alkyl is unsubstituted or substituted with        one to five substituents independently selected from halogen or        hydroxy,    -   C₁₋₆ alkoxy, wherein alkoxy is unsubstituted or substituted with        one to five substituents independently selected from halogen or        hydroxy,    -   C₁₋₆ alkylthio, wherein alkylthio is unsubstituted or        substituted with one to five substituents independently selected        from halogen or hydroxy,    -   C₂₋₆ alkenyl, wherein alkenyl is unsubstituted or substituted        with one to five substituents independently selected from        halogen or hydroxy,    -   (CH₂)_(n)COOH,    -   (CH₂)_(n)COOC₁₋₆ alkyl,    -   (CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ are independently selected        from the group consisting of hydrogen, tetrazolyl, thiazolyl,        (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl,        wherein alkyl is unsubstituted or substituted with one to five        halogens and wherein phenyl and cycloalkyl are unsubstituted or        substituted with one to five substituents independently selected        from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein        alkyl and alkoxy are unsubstituted or substituted with one to        five halogens;        -   or R⁴ and R⁵ together with the nitrogen atom to which they            are attached form a heterocyclic ring selected from            azetidine, pyrrolidine, piperidine, piperazine, and            morpholine wherein said heterocyclic ring is unsubstituted            or substituted with one to five substituents independently            selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,            wherein alkyl and alkoxy are unsubstituted or substituted            with one to five halogens,    -   (CH₂)_(n)—NR⁴R⁵,    -   (CH₂)_(n)—NR⁷COR⁷,    -   (CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted        or substituted with one to three substituents independently        selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens, and    -   (CH₂)_(n)-aryl, wherein aryl is unsubstituted or substituted        with one to five substituents independently selected from        halogen, CN, hydroxy, NR⁷SO₂R⁶, SO₂R⁶, CO₂H, C₁₋₆        alkyloxycarbonyl, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and        alkoxy are unsubstituted or substituted with one to five        halogens;    -   wherein any methylene (CH₂) carbon atom in R¹ or R² is        unsubstituted or substituted with one to two groups        independently selected from halogen, hydroxy, and C₁₋₄ alkyl        unsubstituted or substituted with one to five halogens.

In a class of this embodiment of the compounds of the present invention,R¹ is selected from the group consisting of

-   -   hydrogen,    -   methyl,    -   ethyl,    -   trifluoromethyl,    -   CH₂CF₃,    -   CF₂CF₃,    -   phenyl,    -   cyclopropyl,    -   fluoro,    -   chloro,    -   bromo,    -   vinyl,    -   amino,    -   isopropylamino,    -   acetylamino,    -   2,2,2-trifluoroacetylamino,    -   tert-butylaminocarbonyl,    -   ethoxycarbonyl,    -   carboxy,    -   1-hydroxyethyl,    -   methoxy,    -   isopropoxy, and    -   methylthio.

In a sixth embodiment of the compounds of the present invention, R² isselected from the group consisting of

-   -   hydrogen,    -   halogen,    -   C₁₋₆ alkyl, wherein alkyl is unsubstituted or substituted with        one to five substituents independently selected from halogen or        hydroxy,    -   C₂₋₆ alkenyl, wherein alkenyl is unsubstituted or substituted        with one to five substituents independently selected from        halogen or hydroxy,    -   (CH₂)_(n)COOH,    -   (CH₂)_(n)COOC₁₋₆ alkyl,    -   (CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ are independently selected        from the group consisting of hydrogen, tetrazolyl, thiazolyl,        (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl,        wherein alkyl is unsubstituted or substituted with one to five        halogens and wherein phenyl and cycloalkyl are unsubstituted or        substituted with one to five substituents independently selected        from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein        alkyl and alkoxy are unsubstituted or substituted with one to        five halogens;        -   or R⁴ and R⁵ together with the nitrogen atom to which they            are attached form a heterocyclic ring selected from            azetidine, pyrrolidine, piperidine, piperazine, and            morpholine wherein said heterocyclic ring is unsubstituted            or substituted with one to five substituents independently            selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,            wherein alkyl and alkoxy are unsubstituted or substituted            with one to five halogens,    -   (CH₂)_(n)—NR⁴R⁵,    -   (CH₂)_(n)—NR⁷COR⁷,    -   (CH₂)_(n)—COR⁶,    -   (CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted        or substituted with one to three substituents independently        selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens, and    -   (CH₂)_(n)-aryl, wherein aryl is unsubstituted or substituted        with one to five substituents independently selected from        halogen, cyano, hydroxy, NR₇SO₂R⁶, SO₂R⁶, CO₂H, C₁₋₆        alkyloxycarbonyl, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and        alkoxy are unsubstituted or substituted with one to five        halogens;    -   wherein any methylene (CH₂) carbon atom in R¹ or R² is        unsubstituted or substituted with one to two groups        independently selected from halogen, hydroxy, and C₁₋₄ alkyl        unsubstituted or substituted with one to five halogens.

In a class of this embodiment of the compounds of the present invention,R² is selected from the group consisting of:

-   -   hydrogen    -   trifluoromethyl,    -   phenyl,    -   cyclopropyl,    -   carboxy,    -   ethoxycarbonyl,    -   dimethylaminocarbonyl,    -   aminocarbonyl,    -   morpholin-4-ylcarbonyl,    -   tert-butylaminocarbonyl,    -   cyclopropylcarbonyl,    -   tetrazol-5-ylaminocarbonyl, and    -   2,2,2-trifluoroacetylamino.

In a seventh embodiment of the compounds of the present invention, R⁸,R⁹, and R¹⁰ are independently selected from the group consisting of:

-   -   hydrogen,    -   C₁₋₆ alkyl, unsubstituted or substituted with one to five        substituents independently selected from halogen, hydroxy, C₁₋₆        alkoxy, and phenyl-C₁₋₃ alkoxy, wherein alkoxy is unsubstituted        or substituted with one to five halogens,    -   (CH₂)_(n)-phenyl, wherein phenyl is unsubstituted or substituted        with one to five substituents independently selected from        halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and        alkoxy are unsubstituted or substituted with one to five        halogens,    -   (CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or        substituted with one to three substituents independently        selected from hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are unsubstituted or substituted with        one to five halogens,    -   (CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted or        substituted with one to three substituents independently        selected from oxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆        alkoxy, wherein alkyl and alkoxy are unsubstituted or        substituted with one to five halogens, and    -   (CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted        or substituted with one to three substituents independently        selected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are optionally substituted with one to        five halogens;    -   wherein any methylene (CH₂) carbon atom in R⁸, R⁹, or R¹⁰ is        unsubstituted or substituted with one to two groups        independently selected from halogen, hydroxy, and C₁₋₄ alkyl        unsubstituted or substituted with one to five halogens;        and R₁₁, R¹², and R¹³ are each independently hydrogen or methyl.

In a class of this embodiment of the compounds of the present invention,R⁸, R⁹, and R¹⁰ are each independently selected from the groupconsisting of

-   -   hydrogen,    -   C₁₋₃ alkyl, unsubstituted or substituted with one to three        substituents independently selected from halogen, hydroxy, C₁₋₆        alkoxy, and phenyl-C₁₋₃ alkoxy, wherein alkoxy is unsubstituted        or substituted with one to five halogens,    -   (CH₂)_(n)-phenyl, wherein phenyl is unsubstituted or substituted        with one to five substituents independently selected from        halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and        alkoxy are unsubstituted or substituted with one to five        halogens,    -   (CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or        substituted with one to three substituents independently        selected from hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy,        wherein alkyl and alkoxy are optionally substituted with one to        five halogens, and    -   (CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted or        substituted with one to three substituents independently        selected from oxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆        alkoxy, wherein alkyl and alkoxy are optionally substituted with        one to five halogens,    -   (CH₂)_(n)—C₃₋₆ cyclopropyl;    -   wherein any methylene (CH₂) carbon atom in R⁸, R⁹, or R¹⁰ is        unsubstituted or substituted with one to two groups        independently selected from halogen, hydroxy, and C₁₋₄ alkyl        unsubstituted or substituted with one to five halogens;        and R¹¹, R¹², and R¹³ are each independently hydrogen or methyl.

In a subclass of this class, R⁸, R⁹, and R¹⁰ are each independentlyselected from the group consisting of

hydrogen,

CH₃,

CH₂CH₃,

CH₂-cyclopropyl,

CHF-cyclopropyl,

CH(OH)-cyclopropyl,

CH₂OCH₂Ph,

CH₂(4-F-Ph),

CH₂(4-CF₃-Ph), and

CH₂-[1,2,4]triazol-4-yl;

and R¹¹, R¹², and R¹³ are each independently hydrogen or methyl.

In a further subclass of this class, R⁹, R¹⁰, R¹², and R¹³ are hydrogen.In a subclass of this subclass, R⁸ and R¹¹ are hydrogen.

Illustrative, but nonlimiting examples, of compounds of the presentinvention that are useful as dipeptidyl peptidase-IV inhibitors are thefollowing:

or a pharmaceutically acceptable salt thereof.

As used herein the following definitions are applicable.

“Alkyl”, as well as other groups having the prefix “alk”, such as alkoxyand alkanoyl, means carbon chains which may be linear or branched, andcombinations thereof, unless the carbon chain is defined otherwise.Examples of alkyl groups include methyl, ethyl, propyl, isopropyl,butyl, sec- and tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and thelike. Where the specified number of carbon atoms permits, e.g., fromC₃₋₁₀, the term alkyl also includes cycloalkyl groups, and combinationsof linear or branched alkyl chains combined with cycloalkyl structures.When no number of carbon atoms is specified, C₁₋₆ is intended.

“Cycloalkyl” is a subset of alkyl and means a saturated carbocyclic ringhaving a specified number of carbon atoms. Examples of cycloalkylinclude cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclooctyl, and the like. A cycloalkyl group generally is monocyclicunless stated otherwise. Cycloalkyl groups are saturated unlessotherwise defined.

The term “alkoxy” refers to straight or branched chain alkoxides of thenumber of carbon atoms specified (e.g., C₁₋₁₀ alkoxy), or any numberwithin this range [i.e., methoxy (MeO—), ethoxy, isopropoxy, etc.).

The term “alkylthio” refers to straight or branched chain alkylsulfidesof the number of carbon atoms specified (e.g., C₁₋₁₀ alkylthio), or anynumber within this range [i.e., methylthio (MeS—), ethylthio,isopropylthio, etc.].

The term “alkylamino” refers to straight or branched alkylamines of thenumber of carbon atoms specified (e.g., C₁₋₆ alkylamino), or any numberwithin this range [i.e., methylamino, ethylamino, isopropylamino,t-butylamino, etc.].

The term “alkylsulfonyl” refers to straight or branched chainalkylsulfones of the number of carbon atoms specified (e.g., C₁₋₆alkylsulfonyl), or any number within this range [i.e., methylsulfonyl(MeSO₂—), ethylsulfonyl, isopropylsulfonyl, etc.].

The term “alkyloxycarbonyl” refers to straight or branched chain estersof a carboxylic acid derivative of the present invention of the numberof carbon atoms specified (e.g., C₁₋₆ alkyloxycarbonyl), or any numberwithin this range [i.e., methyloxycarbonyl (MeOCO—), ethyloxycarbonyl,or butyloxycarbonyl].

“Aryl” means a mono- or polycyclic aromatic ring system containingcarbon ring atoms. The preferred aryls are monocyclic or bicyclic 6-10membered aromatic ring systems. Phenyl and naphthyl are preferred aryls.The most preferred aryl is phenyl.

“Heterocycle” and “heterocyclyl” refer to saturated or unsaturatednon-aromatic rings or ring systems containing at least one heteroatomselected from O, S and N, further including the oxidized forms ofsulfur, namely SO and SO₂. Examples of heterocycles includetetrahydrofuran (THF), dihydrofuran, 1,4-dioxane, morpholine,1,4-dithiane, piperazine, piperidine, 1,3-dioxolane, imidazolidine,imidazoline, pyrroline, pyrrolidine, tetrahydropyran, dihydropyran,oxathiolane, dithiolane, 1,3-dioxane, 1,3-dithiane, oxathiane,thiomorpholine, and the like.

“Heteroaryl” means an aromatic or partially aromatic heterocycle thatcontains at least one ring heteroatom selected from O, S and N.Heteroaryls also include heteroaryls fused to other kinds of rings, suchas aryls, cycloalkyls and heterocycles that are not aromatic. Examplesof heteroaryl groups include pyrrolyl, isoxazolyl, isothiazolyl,pyrazolyl, pyridinyl, 2-oxo-(1H)-pyridinyl (2-hydroxy-pyridinyl),oxazolyl, 1,2,4-oxadiazolyl, 1,3,4-oxadiazolyl, thiadiazolyl, thiazolyl,imidazolyl, triazolyl, tetrazolyl, furyl, triazinyl, thienyl,pyrimidinyl, pyrazinyl, benzisoxazolyl, benzoxazolyl, benzothiazolyl,benzothiadiazolyl, dihydrobenzofuranyl, indolinyl, pyridazinyl,indazolyl, isoindolyl, dihydrobenzothienyl, indolizinyl, cinnolinyl,phthalazinyl, quinazolinyl, naphthyridinyl, carbazolyl, benzodioxolyl,quinoxalinyl, purinyl, furazanyl, isobenzylfuranyl, benzimidazolyl,benzofuranyl, benzothienyl, quinolyl, indolyl, isoquinolyl,dibenzofuranyl, imidazo[1,2-a]pyridinyl,[1,2,4-triazolo][4,3-a]pyridinyl, pyrazolo[1,5-a]pyridinyl,[1,2,4-triazolo][1,5-a]pyridinyl, 2-oxo-1,3-benzoxazolyl4-oxo-3H-quinazolinyl, 3-oxo-[1,2,4]-triazolo[4,3-a]-2H-pyridinyl,5-oxo-[1,2,4]-4H-oxadiazolyl, 2-oxo-[1,3,4]-3H-oxadiazolyl,2-oxo-1,3-dihydro-2H-imidazolyl, 3-oxo-2,4-dihydro-3H-1,2,4-triazolyl,and the like. For heterocyclyl and heteroaryl groups, rings and ringsystems containing from 3-15 atoms are included, forming 1-3 rings.

“Halogen” refers to fluorine, chlorine, bromine and iodine. Chlorine andfluorine are generally preferred. Fluorine is most preferred when thehalogens are substituted on an alkyl or alkoxy group (e.g. CF₃O andCF₃CH₂O).

The compounds of the present invention may contain one or moreasymmetric centers and can thus occur as racemates and racemic mixtures,single enantiomers, diastereomeric mixtures and individualdiastereomers. The compounds of the present invention have oneasymmetric center at the carbon atom marked with an * in formula Ia.Additional asymmetric centers may be present depending upon the natureof the various substituents on the molecule. Each such asymmetric centerwill independently produce two optical isomers and it is intended thatall of the possible optical isomers and diastereomers in mixtures and aspure or partially purified compounds are included within the ambit ofthis invention. The present invention is meant to comprehend all suchisomeric forms of these compounds.

Some of the compounds described herein contain olefinic double bonds,and unless specified otherwise, are meant to include both E and Zgeometric isomers.

Some of the compounds described herein may exist as tautomers, whichhave different points of attachment of hydrogen accompanied by one ormore double bond shifts. For example, a ketone and its enol form areketo-enol tautomers. The individual tautomers as well as mixturesthereof are encompassed with compounds of the present invention.

Formula I shows the structure of the class of compounds withoutpreferred stereochemistry. Formula Ia shows the preferred sterochemistryat the carbon atom to which is attached the amino group of the betaamino acid from which these compounds are prepared.

The independent syntheses of these diastereomers or theirchromatographic separations may be achieved as known in the art byappropriate modification of the methodology disclosed herein. Theirabsolute stereochemistry may be determined by the x-ray crystallographyof crystalline products or crystalline intermediates which arederivatized, if necessary, with a reagent containing an asymmetriccenter of known absolute configuration.

If desired, racemic mixtures of the compounds may be separated so thatthe individual enantiomers are isolated. The separation can be carriedout by methods well known in the art, such as the coupling of a racemicmixture of compounds to an enantiomerically pure compound to form adiastereomeric mixture, followed by separation of the individualdiastereomers by standard methods, such as fractional crystallization orchromatography. The coupling reaction is often the formation of saltsusing an enantiomerically pure acid or base. The diasteromericderivatives may then be converted to the pure enantiomers by cleavage ofthe added chiral residue. The racemic mixture of the compounds can alsobe separated directly by chromatographic methods utilizing chiralstationary phases, which methods are well known in the art.

Alternatively, any enantiomer of a compound may be obtained bystereoselective synthesis using optically pure starting materials orreagents of known configuration by methods well known in the art.

It will be understood that, as used herein, references to the compoundsof structural formula I are meant to also include the pharmaceuticallyacceptable salts, and also salts that are not pharmaceuticallyacceptable when they are used as precursors to the free compounds ortheir pharmaceutically acceptable salts or in other syntheticmanipulations.

The compounds of the present invention may be administered in the formof a pharmaceutically acceptable salt. The term “pharmaceuticallyacceptable salt” refers to salts prepared from pharmaceuticallyacceptable non-toxic bases or acids including inorganic or organic basesand inorganic or organic acids. Salts of basic compounds encompassedwithin the term “pharmaceutically acceptable salt” refer to non-toxicsalts of the compounds of this invention which are generally prepared byreacting the free base with a suitable organic or inorganic acid.Representative salts of basic compounds of the present inventioninclude, but are not limited to, the following: acetate,benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate,bromide, camsylate, carbonate, chloride, clavulanate, citrate,dihydrochloride, edetate, edisylate, estolate, esylate, fumarate,gluceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate,hydrabamine, hydrobromide, hydrochloride, hydroxynaphthoate, iodide,isothionate, lactate, lactobionate, laurate, malate, maleate, mandelate,mesylate, methylbromide, methylnitrate, methylsulfate, mucate,napsylate, nitrate, N-methylglucamine ammonium salt, oleate, oxalate,pamoate (embonate), palmitate, pantothenate, phosphate/diphosphate,polygalacturonate, salicylate, stearate, sulfate, subacetate, succinate,tannate, tartrate, teoclate, tosylate, triethiodide and valerate.Furthermore, where the compounds of the invention carry an acidicmoiety, suitable pharmaceutically acceptable salts thereof include, butare not limited to, salts derived from inorganic bases includingaluminum, ammonium, calcium, copper, ferric, ferrous, lithium,magnesium, manganic, mangamous, potassium, sodium, zinc, and the like.Particularly preferred are the ammonium, calcium, magnesium, potassium,and sodium salts. Salts derived from pharmaceutically acceptable organicnon-toxic bases include salts of primary, secondary, and tertiaryamines, cyclic amines, and basic ion-exchange resins, such as arginine,betaine, caffeine, choline, N,N-dibenzylethylenediamine, diethylamine,2-diethylaminoethanol, 2-dimethylaminoethanol, ethanolamine,ethylenediamine, N-ethylmorpholine, N-ethylpiperidine, glucamine,glucosamine, histidine, hydrabamine, isopropylamine, lysine,methylglucamine, morpholine, piperazine, piperidine, polyamine resins,procaine, purines, theobromine, triethylamine, trimethylamine,tripropylamine, tromethamine, and the like.

Also, in the case of a carboxylic acid (—COOH) or alcohol group beingpresent in the compounds of the present invention, pharmaceuticallyacceptable esters of carboxylic acid derivatives, such as methyl, ethyl,or pivaloyloxymethyl, or acyl derivatives of alcohols, such as acetateor maleate, can be employed. Included are those esters and acyl groupsknown in the art for modifying the solubility or hydrolysischaracteristics for use as sustained-release or prodrug formulations.

Solvates, and in particular, the hydrates of the compounds of structuralformula I are included in the present invention as well.

Exemplifying the invention is the use of the compounds disclosed in theExamples and herein.

The subject compounds are useful in a method of inhibiting thedipeptidyl peptidase-IV enzyme in a patient such as a mammal in need ofsuch inhibition comprising the administration of an effective amount ofthe compound. The present invention is directed to the use of thecompounds disclosed herein as inhibitors of dipeptidyl peptidase-IVenzyme activity.

In addition to primates, such as humans, a variety of other mammals canbe treated according to the method of the present invention. Forinstance, mammals including, but not limited to, cows, sheep, goats,horses, dogs, cats, guinea pigs, rats or other bovine, ovine, equine,canine, feline, rodent or murine species can be treated. However, themethod can also be practiced in other species, such as avian species(e.g., chickens).

The present invention is further directed to a method for themanufacture of a medicament for inhibiting dipeptidyl peptidase-IVenzyme activity in humans and animals comprising combining a compound ofthe present invention with a pharmaceutically acceptable carrier ordiluent.

The subject treated in the present methods is generally a mammal,preferably a human being, male or female, in whom inhibition ofdipeptidyl peptidase-IV enzyme activity is desired. The term“therapeutically effective amount” means the amount of the subjectcompound that will elicit the biological or medical response of atissue, system, animal or human that is being sought by the researcher,veterinarian, medical doctor or other clinician.

The term “composition” as used herein is intended to encompass a productcomprising the specified ingredients in the specified amounts, as wellas any product which results, directly or indirectly, from combinationof the specified ingredients in the specified amounts. Such term inrelation to pharmaceutical composition, is intended to encompass aproduct comprising the active ingredient(s), and the inert ingredient(s)that make up the carrier, as well as any product which results, directlyor indirectly, from combination, complexation or aggregation of any twoor more of the ingredients, or from dissociation of one or more of theingredients, or from other types of reactions or interactions of one ormore of the ingredients. Accordingly, the pharmaceutical compositions ofthe present invention encompass any composition made by admixing acompound of the present invention and a pharmaceutically acceptablecarrier. By “pharmaceutically acceptable” it is meant the carrier,diluent or excipient must be compatible with the other ingredients ofthe formulation and not deleterious to the recipient thereof.

The terms “administration of” and or “administering a” compound shouldbe understood to mean providing a compound of the invention or a prodrugof a compound of the invention to the individual in need of treatment.

The utility of the compounds in accordance with the present invention asinhibitors of dipeptidyl peptidase-IV enzyme activity may bedemonstrated by methodology known in the art. Inhibition constants aredetermined as follows. A continuous fluorometric assay is employed withthe substrate Gly-Pro-AMC, which is cleaved by DP-IV to release thefluorescent AMC leaving group. The kinetic parameters that describe thisreaction are as follows: K_(m)=50 μM; k_(cat)=75 s⁻¹;k_(cat)/K_(m)=1.5×10⁶ M⁻¹s⁻¹. A typical reaction contains approximately50 pM enzyme, 50 μM Gly-Pro-AMC, and buffer (100 mM HEPES, pH 7.5, 0.1mg/ml BSA) in a total reaction volume of 100 μl. Liberation of AMC ismonitored continuously in a 96-well plate fluorometer using anexcitation wavelength of 360 nm and an emission wavelength of 460 nm.Under these conditions, approximately 0.8 μM AMC is produced in 30minutes at 25 degrees C. The enzyme used in these studies was soluble(transmembrane domain and cytoplasmic extension excluded) human proteinproduced in a baculovirus expression system (Bac-To-Bac, Gibco BRL). Thekinetic constants for hydrolysis of Gly-Pro-AMC and GLP-1 were found tobe in accord with literature values for the native enzyme. To measurethe dissociation constants for compounds, solutions of inhibitor in DMSOwere added to reactions containing enzyme and substrate (final DMSOconcentration is 1%). All experiments were conducted at room temperatureusing the standard reaction conditions described above. To determine thedissociation constants (K_(i)), reaction rates were fit by non-linearregression to the Michaelis-Menton equation for competitive inhibition.The errors in reproducing the dissociation constants are typically lessthan two-fold.

In particular, the compounds of the following examples had activity ininhibiting the dipeptidyl peptidase-IV enzyme in the aforementionedassays, generally with an IC₅₀ of less than about 1 μM. Such a result isindicative of the intrinsic activity of the compounds in use asinhibitors the dipeptidyl peptidase-IV enzyme activity.

Dipeptidyl peptidase-IV enzyme (DP-IV) is a cell surface protein thathas been implicated in a wide range of biological functions. It has abroad tissue distribution (intestine, kidney, liver, pancreas, placenta,thymus, spleen, epithelial cells, vascular endothelium, lymphoid andmyeloid cells, serum), and distinct tissue and cell-type expressionlevels. DP-IV is identical to the T cell activation marker CD26, and itcan cleave a number of immunoregulatory, endocrine, and neurologicalpeptides in vitro. This has suggested a potential role for thispeptidase in a variety of disease processes in humans or other species.

Accordingly, the subject compounds are useful in a method for theprevention or treatment of the following diseases, disorders andconditions.

Type II Diabetes and Related Disorders: It is well established that theincretins GLP-1 and GIP are rapidly inactivated in vivo by DP-IV.Studies with DP-IV^((−/−))-deficient mice and preliminary clinicaltrials indicate that DP-IV inhibition increases the steady stateconcentrations of GLP-1 and GIP, resulting in improved glucosetolerance. By analogy to GLP-1 and GIP, it is likely that other glucagonfamily peptides involved in glucose regulation are also inactivated byDP-IV (eg. PACAP). Inactivation of these peptides by DP-IV may also playa role in glucose homeostasis.

The DP-IV inhibitors of the present invention therefore have utility inthe treatment of type II diabetes and in the treatment and prevention ofthe numerous conditions that often accompany Type II diabetes, includingmetabolic syndrome X, reactive hypoglycemia, and diabetic dyslipidemia.Obesity, discussed below, is another condition that is often found withType II diabetes that may respond to treatment with the compounds ofthis invention.

The following diseases, disorders and conditions are related to Type 2diabetes, and therefore may be treated, controlled or in some casesprevented, by treatment with the compounds of this invention: (1)hyperglycemia, (2) low glucose tolerance, (3) insulin resistance, (4)obesity, (5) lipid disorders, (6) dyslipidemia, (7) hyperlipidemia, (8)hypertriglyceridemia, (9) hypercholesterolemia, (10) low HDL levels,(11) high LDL levels, (12) atherosclerosis and its sequelae, (13)vascular restenosis, (14) irritable bowel syndrome, (15) inflammatorybowel disease, including Crohn's disease and ulcerative colitis, (16)other inflammatory conditions, (17) pancreatitis, (18) abdominalobesity, (19) neurodegenerative disease, (20) retinopathy, (21)nephropathy, (22) neuropathy, (23) Syndrome X, (24) ovarianhyperandrogenism (polycystic ovarian syndrome), and other disorderswhere insulin resistance is a component.

Obesity: DP-IV inhibitors may be useful for the treatment of obesity.This is based on the observed inhibitory effects on food intake andgastric emptying of GLP-1 and GLP-2. Exogenous administration of GLP-1in humans significantly decreases food intake and slows gastric emptying(Am. J. Physiol., 277: R910-R916 (1999)). ICV administration of GLP-1 inrats and mice also has profound effects on food intake (Nature Medicine,2: 1254-1258 (1996)). This inhibition of feeding is not observed inGLP-1R^((−/−)) mice, indicating that these effects are mediated throughbrain GLP-1 receptors. By analogy to GLP-1, it is likely that GLP-2 isalso regulated by DP-IV. ICV administration of GLP-2 also inhibits foodintake, analogous to the effects observed with GLP-1 (Nature Medicine,6: 802-807 (2000)). In addition, studies with DP-IV deficient micesuggest that these animals are resistant to diet-induced obesity andassociated pathology (e.g. hyperinsulinonemia).

Growth Hormone Deficiency: DP-IV inhibition may be useful for thetreatment of growth hormone deficiency, based on the hypothesis thatgrowth-hormone releasing factor (GRF), a peptide that stimulates releaseof growth hormone from the anterior pituitary, is cleaved by the DP-IVenzyme in vivo (WO 00/56297). The following data provide evidence thatGRF is an endogenous substrate: (1) GRF is efficiently cleaved in vitroto generate the inactive product GRF[3-44] (BBA 1122: 147-153 (1992));(2) GRF is rapidly degraded in plasma to GRF[3-44]; this is prevented bythe DP-IV inhibitor diprotin A; and (3) GRF[3-44] is found in the plasmaof a human GRF transgenic pig (J. Clin. Invest., 83:1533-1540 (1989)).Thus DP-IV inhibitors may be useful for the same spectrum of indicationswhich have been considered for growth hormone secretagogues.

Intestinal Injury: The potential for using DP-IV inhibitors for thetreatment of intestinal injury is suggested by the results of studiesindicating that glucagon-like peptide-2 (GLP-2), a likely endogenoussubstrate for DP-IV, may exhibit trophic effects on the intestinalepithelium (Regulatory Peptides, 90: 27-32 (2000)). Administration ofGLP-2 results in increased small bowel mass in rodents and attenuatesintestinal injury in rodent models of colitis and enteritis.

Immunosuppression: DP-IV inhibition may be useful for modulation of theimmune response, based upon studies implicating the DP-IV enzyme in Tcell activation and in chemokine processing, and efficacy of DP-IVinhibitors in in vivo models of disease. DP-IV has been shown to beidentical to CD26, a cell surface marker for activated immune cells. Theexpression of CD26 is regulated by the differentiation and activationstatus of immune cells. It is generally accepted that CD26 functions asa co-stimulatory molecule in in vitro models of T cell activation. Anumber of chemokines contain proline in the penultimate position,presumably to protect them from degradation by non-specificaminopeptidases. Many of these have been shown to be processed in vitroby DP-IV. In several cases (RANTES, LD78-beta, MDC, eotaxin,SDF-1alpha), cleavage results in an altered activity in chemotaxis andsignaling assays. Receptor selectivity also appears to be modified insome cases (RANTES). Multiple N-terminally truncated forms of a numberof chemokines have been identified in in vitro cell culture systems,including the predicted products of DP-IV hydrolysis.

DP-IV inhibitors have been shown to be efficacious immunosupressants inanimal models of transplantation and arthritis. Prodipine(Pro-Pro-diphenyl-phosphonate), an irreversible inhibitor of DP-IV, wasshown to double cardiac allograft survival in rats from day 7 to day 14(Transplantation, 63: 1495-1500 (1997)). DP-IV inhibitors have beentested in collagen and alkyldiamine-induced arthritis in rats and showeda statistically significant attenuation of hind paw swelling in thismodel [Int. J. Immunopharmacology, 19:15-24 (1997) andImmunopharmacology, 40: 21-26 (1998)]. DP-IV is upregulated in a numberof autoimmune diseases including rheumatoid arthritis, multiplesclerosis, Graves' disease, and Hashimoto's thyroiditis (ImmunologyToday, 20: 367-375 (1999)).

HIV Infection: DP-IV inhibition may be useful for the treatment orprevention of HIV infection or AIDS because a number of chemokines whichinhibit HIV cell entry are potential substrates for DP-IV (ImmunologyToday 20: 367-375 (1999)). In the case of SDF-1alpha, cleavage decreasesantiviral activity (PNAS, 95: 6331-6 (1998)). Thus, stabilization ofSDF-1alpha through inhibition of DP-IV would be expected to decrease HIVinfectivity.

Hematopoiesis: DP-IV inhibition may be useful for the treatment orprevention of hematopiesis because DP-IV may be involved inhematopoiesis. A DP-IV inhibitor, Val-Boro-Pro, stimulated hematopoiesisin a mouse model of cyclophosphamide-induced neutropenia (WO 99/56753).

Neuronal Disorders: DP-IV inhibition may be useful for the treatment orprevention of various neuronal or psychiatric disorders because a numberof peptides implicated in a variety of neuronal processes are cleaved invitro by DP-IV. A DP-IV inhibitor thus may have a therapeutic benefit inthe treatment of neuronal disorders. Endomorphin-2, beta-casomorphin,and substance P have all been shown to be in vitro substrates for DP-IV.In all cases, in vitro cleavage is highly efficient, withk_(cat)/K_(m)˜10⁶ M⁻¹s⁻¹ or greater. In an electric shock jump testmodel of analgesia in rats, a DP-IV inhibitor showed a significanteffect that was independent of the presence of exogenous endomorphin-2(Brain Research, 815: 278-286 (1999)). Neuroprotective andneuroregenerative effects of DP-IV inhibitors were also evidenced by theinhibitors' ability to protect motor neurons from excitotoxic celldeath, to protect striatal innervation of dopaminergic neurons whenadministered concurrently with MPTP, and to promote recovery of striatalinnervation density when given in a therapeutic manner following MPTPtreatment [see Yong-Q. Wu, et al., “Neuroprotective Effects ofInhibitors of Dipeptidyl Peptidase-IV In Vitro and In Vivo,” Int. Conf.On Dipeptidyl Aminopeptidases: Basic Science and Clinical Applications,Sep. 26-29, 2002 (Berlin, Germany)).

Tumor Invasion and Metastasis: DP-IV inhibition may be useful for thetreatment or prevention of tumor invasion and metastasis because anincrease or decrease in expression of several ectopeptidases includingDP-IV has been observed during the transformation of normal cells to amalignant phenotype (J. Exp. Med., 190: 301-305 (1999)). Up- ordown-regulation of these proteins appears to be tissue and cell-typespecific. For example, increased CD26/DP-IV expression has been observedon T cell lymphoma, T cell acute lymphoblastic leukemia, cell-derivedthyroid carcinomas, basal cell carcinomas, and breast carcinomas. Thus,DP-IV inhibitors may have utility in the treatment of such carcinomas.

Benign Prostatic Hypertrophy: DP-IV inhibition may be useful for thetreatment of benign prostatic hypertrophy because increased DP-IVactivity was noted in prostate tissue from patients with BPH (Eur. J.Clin. Chem. Clin. Biochem., 30: 333-338 (1992)).

Sperm motility/male contraception: DP-IV inhibition may be useful forthe altering sperm motility and for male contraception because inseminal fluid, prostatosomes, prostate derived organelles important forsperm motility, possess very high levels of DP-IV activity (Eur. J.Clin. Chem. Clin. Biochem., 30: 333-338 (1992)).

Gingivitis: DP-IV inhibition may be useful for the treatment ofgingivitis because DP-IV activity was found in gingival crevicular fluidand in some studies correlated with periodontal disease severity (Arch.Oral Biol., 37: 167-173 (1992)).

Osteoporosis: DP-IV inhibition may be useful for the treatment orprevention of osteoporosis because GIP receptors are present inosteoblasts.

The compounds of the present invention have utility in treating orpreventing one or more of the following conditions or diseases: (1)hyperglycemia, (2) low glucose tolerance, (3) insulin resistance, (4)obesity, (5) lipid disorders, (6) dyslipidemia, (7) hyperlipidemia, (8)hypertriglyceridemia, (9) hypercholesterolemia, (10) low HDL levels,(11) high LDL levels, (12) atherosclerosis and its sequelae, (13)vascular restenosis, (14) irritable bowel syndrome, (15) inflammatorybowel disease, including Crohn's disease and ulcerative colitis, (16)other inflammatory conditions, (17) pancreatitis, (18) abdominalobesity, (19) neurodegenerative disease, (20) retinopathy, (21)nephropathy, (22) neuropathy, (23) Syndrome X, (24) ovarianhyperandrogenism (polycystic ovarian syndrome), (25) Type II diabetes,(26) growth hormone deficiency, (27) neutropenia, (28) neuronaldisorders, (29) tumor metastasis, (30) benign prostatic hypertrophy,(32) gingivitis, (33) hypertension, (34) osteoporosis, and otherconditions that may be treated or prevented by inhibition of DP-IV.

The subject compounds are further useful in a method for the preventionor treatment of the aforementioned diseases, disorders and conditions incombination with other agents.

The compounds of the present invention may be used in combination withone or more other drugs in the treatment, prevention, suppression oramelioration of diseases or conditions for which compounds of Formula Ior the other drugs may have utility, where the combination of the drugstogether are safer or more effective than either drug alone. Such otherdrug(s) may be administered, by a route and in an amount commonly usedtherefor, contemporaneously or sequentially with a compound of FormulaI. When a compound of Formula I is used contemporaneously with one ormore other drugs, a pharmaceutical composition in unit dosage formcontaining such other drugs and the compound of Formula I is preferred.However, the combination therapy may also includes therapies in whichthe compound of Formula I and one or more other drugs are administeredon different overlapping schedules. It is also contemplated that whenused in combination with one or more other active ingredients, thecompounds of the present invention and the other active ingredients maybe used in lower doses than when each is used singly. Accordingly, thepharmaceutical compositions of the present invention include those thatcontain one or more other active ingredients, in addition to a compoundof Formula I.

Examples of other active ingredients that may be administered incombination with a compound of Formula I, and either administeredseparately or in the same pharmaceutical composition, include, but arenot limited to:

(a) other dipeptidyl peptidase IV (DP-IV) inhibitors;

(b) insulin sensitizers including (i) PPARγ agonists such as theglitazones (e.g. troglitazone, pioglitazone, englitazone, MCC-555,rosiglitazone, and the like) and other PPAR ligands, including PPARα/γdual agonists, such as KRP-297, and PPARα agonists such as fenofibricacid derivatives (gemfibrozil, clofibrate, fenofibrate and bezafibrate),(ii) biguanides such as metformin and phenformin, and (iii) proteintyrosine phosphatase-1B (PTP-1B) inhibitors;

(c) insulin or insulin mimetics;

(d) sulfonylureas and other insulin secretagogues, such as tolbutamideglyburide, glipizide, glimepiride, and meglitinides, such asrepaglinide;

(e) α-glucosidase inhibitors (such as acarbose and miglitol);

(f) glucagon receptor antagonists such as those disclosed in WO98/04528, WO 99/01423, WO 00/39088, and WO 00/69810;

(g) GLP-1, GLP-1 mimetics, and GLP-1 receptor agonists such as thosedisclosed in WO00/42026 and WO00/59887;

(h) GIP and GIP mimetics such as those disclosed in WO00/58360, and GIPreceptor agonists;

(i) PACAP, PACAP mimetics, and PACAP receptor agonists such as thosedisclosed in WO 01/23420;

(j) cholesterol lowering agents such as (i) HMG-CoA reductase inhibitors(lovastatin, simvastatin, pravastatin, cerivastatin, fluvastatin,atorvastatin, itavastatin, and rosuvastatin, and other statins), (ii)sequestrants (cholestyramine, colestipol, and dialkylaminoalkylderivatives of a cross-linked dextran), (iii) nicotinyl alcohol,nicotinic acid or a salt thereof, (iv) PPARα agonists such as fenofibricacid derivatives (gemfibrozil, clofibrate, fenofibrate and bezafibrate),(v) PPARα/γ dual agonists, such as KRP-297, (vi) inhibitors ofcholesterol absorption, such as beta-sitosterol and ezetimibe, (vii)acyl CoA:cholesterol acyltransferase inhibitors, such as avasimibe, and(viii) anti-oxidants, such as probucol;

(k) PPARδ agonists, such as those disclosed in WO097/28149;

(l) antiobesity compounds such as fenfluramine, dexfenfluramine,phentermine, sibutramine, orlistat, neuropeptide Y5 inhibitors,cannabinoid-1 (CB-1) receptor antagonists/reverse agonists,melanocortin-4 receptor agonists, and β₃ adrenergic receptor agonists;

(m) ileal bile acid transporter inhibitors;

(n) agents intended for use in inflammatory conditions such as aspirin,non-steroidal anti-inflammatory drugs, glucocorticoids, azulfidine, andselective cyclooxygenase-2 inhibitors; and

(o) antihypertensive agents such as ACE inhibitors (enalapril,lisinopril, captopril, quinapril, tandolapril), A-II receptor blockers(losartan, candesartan, irbesartan, valsartan, telmisartan, eprosartan),beta blockers and calcium channel blockers.

The above combinations include combinations of a compound of the presentinvention not only with one other active compound, but also with two ormore other active compounds. Non-limiting examples include combinationsof compounds having Formula I with two or more active compounds selectedfrom biguanides, sulfonylureas, HMG-CoA reductase inhibitors, PPARagonists, PTP-1B inhibitors, other DP-IV inhibitors, and anti-obesitycompounds.

Likewise, compounds of the present invention may be used in combinationwith other drugs that are used in the treatment/prevention/suppressionor amelioration of the diseases or conditions for which compounds of thepresent invention are useful. Such other drugs may be administered, by aroute and in an amount commonly used therefor, contemporaneously orsequentially with a compound of the present invention. When a compoundof the present invention is used contemporaneously with one or moreother drugs, a pharmaceutical composition containing such other drugs inaddition to the compound of the present invention is preferred.Accordingly, the pharmaceutical compositions of the present inventioninclude those that also contain one or more other active ingredients, inaddition to a compound of the present invention.

The weight ratio of the compound of the present invention to the secondactive ingredient may be varied and will depend upon the effective doseof each ingredient. Generally, an effective dose of each will be used.Thus, for example, when a compound of the present invention is combinedwith another agent, the weight ratio of the compound of the presentinvention to the other agent will generally range from about 1000:1 toabout 1:1000, preferably about 200:1 to about 1:200. Combinations of acompound of the present invention and other active ingredients willgenerally also be within the aforementioned range, but in each case, aneffective dose of each active ingredient should be used.

In such combinations the compound of the present invention and otheractive agents may be administered separately or in conjunction. Inaddition, the administration of one element may be prior to, concurrentto, or subsequent to the administration of other agent(s).

The compounds of the present invention may be administered by oral,parenteral (e.g., intramuscular, intraperitoneal, intravenous, ICV,intracisternal injection or infusion, subcutaneous injection, orimplant), by inhalation spray, nasal, vaginal, rectal, sublingual, ortopical routes of administration and may be formulated, alone ortogether, in suitable dosage unit formulations containing conventionalnon-toxic pharmaceutically acceptable carriers, adjuvants and vehiclesappropriate for each route of administration. In addition to thetreatment of warm-blooded animals such as mice, rats, horses, cattle,sheep, dogs, cats, monkeys, etc., the compounds of the invention areeffective for use in humans.

The pharmaceutical compositions for the administration of the compoundsof this invention may conveniently be presented in dosage unit form andmay be prepared by any of the methods well known in the art of pharmacy.All methods include the step of bringing the active ingredient intoassociation with the carrier which constitutes one or more accessoryingredients. In general, the pharmaceutical compositions are prepared byuniformly and intimately bringing the active ingredient into associationwith a liquid carrier or a finely divided solid carrier or both, andthen, if necessary, shaping the product into the desired formulation. Inthe pharmaceutical composition the active object compound is included inan amount sufficient to produce the desired effect upon the process orcondition of diseases. As used herein, the term “composition” isintended to encompass a product comprising the specified ingredients inthe specified amounts, as well as any product which results, directly orindirectly, from combination of the specified ingredients in thespecified amounts.

The pharmaceutical compositions containing the active ingredient may bein a form suitable for oral use, for example, as tablets, troches,lozenges, aqueous or oily suspensions, dispersible powders or granules,emulsions, hard or soft capsules, or syrups or elixirs. Compositionsintended for oral use may be prepared according to any method known tothe art for the manufacture of pharmaceutical compositions and suchcompositions may contain one or more agents selected from the groupconsisting of sweetening agents, flavoring agents, coloring agents andpreserving agents in order to provide pharmaceutically elegant andpalatable preparations. Tablets contain the active ingredient inadmixture with non-toxic pharmaceutically acceptable excipients whichare suitable for the manufacture of tablets. These excipients may be forexample, inert diluents, such as calcium carbonate, sodium carbonate,lactose, calcium phosphate or sodium phosphate; granulating anddisintegrating agents, for example, corn starch, or alginic acid;binding agents, for example starch, gelatin or acacia, and lubricatingagents, for example magnesium stearate, stearic acid or talc. Thetablets may be uncoated or they may be coated by known techniques todelay disintegration and absorption in the gastrointestinal tract andthereby provide a sustained action over a longer period. For example, atime delay material such as glyceryl monostearate or glyceryl distearatemay be employed. They may also be coated by the techniques described inthe U.S. Pat. Nos. 4,256,108; 4,166,452; and 4,265,874 to form osmotictherapeutic tablets for control release.

Formulations for oral use may also be presented as hard gelatin capsuleswherein the active ingredient is mixed with an inert solid diluent, forexample, calcium carbonate, calcium phosphate or kaolin, or as softgelatin capsules wherein the active ingredient is mixed with water or anoil medium, for example peanut oil, liquid paraffin, or olive oil.

Aqueous suspensions contain the active materials in admixture withexcipients suitable for the manufacture of aqueous suspensions. Suchexcipients are suspending agents, for example sodiumcarboxymethylcellulose, methylcellulose, hydroxy-propylmethylcellulose,sodium alginate, polyvinyl-pyrrolidone, gum tragacanth and gum acacia;dispersing or wetting agents may be a naturally-occurring phosphatide,for example lecithin, or condensation products of an alkylene oxide withfatty acids, for example polyoxyethylene stearate, or condensationproducts of ethylene oxide with long chain aliphatic alcohols, forexample heptadecaethyleneoxycetanol, or condensation products ofethylene oxide with partial esters derived from fatty acids and ahexitol such as polyoxyethylene sorbitol monooleate, or condensationproducts of ethylene oxide with partial esters derived from fatty acidsand hexitol anhydrides, for example polyethylene sorbitan monooleate.The aqueous suspensions may also contain one or more preservatives, forexample ethyl, or n-propyl, p-hydroxybenzoate, one or more coloringagents, one or more flavoring agents, and one or more sweetening agents,such as sucrose or saccharin.

Oily suspensions may be formulated by suspending the active ingredientin a vegetable oil, for example arachis oil, olive oil, sesame oil orcoconut oil, or in a mineral oil such as liquid paraffin. The oilysuspensions may contain a thickening agent, for example beeswax, hardparaffin or cetyl alcohol. Sweetening agents such as those set forthabove, and flavoring agents may be added to provide a palatable oralpreparation. These compositions may be preserved by the addition of ananti-oxidant such as ascorbic acid.

Dispersible powders and granules suitable for preparation of an aqueoussuspension by the addition of water provide the active ingredient inadmixture with a dispersing or wetting agent, suspending agent and oneor more preservatives. Suitable dispersing or wetting agents andsuspending agents are exemplified by those already mentioned above.Additional excipients, for example sweetening, flavoring and coloringagents, may also be present.

The pharmaceutical compositions of the invention may also be in the formof oil-in-water emulsions. The oily phase may be a vegetable oil, forexample olive oil or arachis oil, or a mineral oil, for example liquidparaffin or mixtures of these. Suitable emulsifying agents may benaturally-occurring gums, for example gum acacia or gum tragacanth,naturally-occurring phosphatides, for example soy bean, lecithin, andesters or partial esters derived from fatty acids and hexitolanhydrides, for example sorbitan monooleate, and condensation productsof the said partial esters with ethylene oxide, for examplepolyoxyethylene sorbitan monooleate. The emulsions may also containsweetening and flavoring agents.

Syrups and elixirs may be formulated with sweetening agents, for exampleglycerol, propylene glycol, sorbitol or sucrose. Such formulations mayalso contain a demulcent, a preservative and flavoring and coloringagents.

The pharmaceutical compositions may be in the form of a sterileinjectable aqueous or oleagenous suspension. This suspension may beformulated according to the known art using those suitable dispersing orwetting agents and suspending agents which have been mentioned above.The sterile injectable preparation may also be a sterile injectablesolution or suspension in a non-toxic parenterally-acceptable diluent orsolvent, for example as a solution in 1,3-butane diol. Among theacceptable vehicles and solvents that may be employed are water,Ringer's solution and isotonic sodium chloride solution. In addition,sterile, fixed oils are conventionally employed as a solvent orsuspending medium. For this purpose any bland fixed oil may be employedincluding synthetic mono- or diglycerides. In addition, fatty acids suchas oleic acid find use in the preparation of injectables.

The compounds of the present invention may also be administered in theform of suppositories for rectal administration of the drug. Thesecompositions can be prepared by mixing the drug with a suitablenon-irritating excipient which is solid at ordinary temperatures butliquid at the rectal temperature and will therefore melt in the rectumto release the drug. Such materials are cocoa butter and polyethyleneglycols.

For topical use, creams, ointments, jellies, solutions or suspensions,etc., containing the compounds of The present invention are employed.(For purposes of this application, topical application shall includemouth washes and gargles.)

The pharmaceutical composition and method of the present invention mayfurther comprise other therapeutically active compounds as noted hereinwhich are usually applied in the treatment of the above mentionedpathological conditions.

In the treatment or prevention of conditions which require inhibition ofdipeptidyl peptidase-IV enzyme activity an appropriate dosage level willgenerally be about 0.01 to 500 mg per kg patient body weight per daywhich can be administered in single or multiple doses. Preferably, thedosage level will be about 0.1 to about 250 mg/kg per day; morepreferably about 0.5 to about 100 mg/kg per day. A suitable dosage levelmay be about 0.01 to 250 mg/kg per day, about 0.05 to 100 mg/kg per day,or about 0.1 to 50 mg/kg per day. Within this range the dosage may be0.05 to 0.5, 0.5 to 5 or 5 to 50 mg/kg per day. For oral administration,the compositions are preferably provided in the form of tabletscontaining 1.0 to 1000 mg of the active ingredient, particularly 1.0,5.0, 10.0, 15.0. 20.0, 25.0, 50.0, 75.0, 100.0, 150.0, 200.0, 250.0,300.0, 400.0, 500.0, 600.0, 750.0, 800.0, 900.0, and 1000.0 mg of theactive ingredient for the symptomatic adjustment of the dosage to thepatient to be treated. The compounds may be administered on a regimen of1 to 4 times per day, preferably once or twice per day.

When treating or preventing diabetes mellitus and/or hyperglycemia orhypertriglyceridemia or other diseases for which compounds of thepresent invention are indicated, generally satisfactory results areobtained when the compounds of the present invention are administered ata daily dosage of from about 0.1 mg to about 100 mg per kilogram ofanimal body weight, preferably given as a single daily dose or individed doses two to six times a day, or in sustained release form. Formost large mammals, the total daily dosage is from about 1.0 mg to about1000 mg, preferably from about 1 mg to about 50 mg. In the case of a 70kg adult human, the total daily dose will generally be from about 7 mgto about 350 mg. This dosage regimen may be adjusted to provide theoptimal therapeutic response.

It will be understood, however, that the specific dose level andfrequency of dosage for any particular patient may be varied and willdepend upon a variety of factors including the activity of the specificcompound employed, the metabolic stability and length of action of thatcompound, the age, body weight, general health, sex, diet, mode and timeof administration, rate of excretion, drug combination, the severity ofthe particular condition, and the host undergoing therapy.

Several methods for preparing the compounds of this invention areillustrated in the following Schemes and Examples. Starting materialsare made according to procedures known in the art or as illustratedherein.

The compounds of the present invention can be prepared from beta aminoacid intermediates such as those of formula II and substitutedheterocyclic intermediates such as those of formula III, using standardpeptide coupling conditions followed by deprotection. The preparation ofthese intermediates is described in the following schemes.

where Ar, X, R¹, R⁸, R⁹, R¹⁰, R¹¹, R¹² and R¹³ are as defined above andP is a suitable nitrogen protecting group such as tert-butoxycarbonyl,benzyloxycarbonyl, and 9-fluorenylmethoxycarbonyl.

Compounds of formula II are commercially available, known in theliterature or may be conveniently prepared by a variety of methodsfamiliar to those skilled in the art. One common route is illustrated inScheme 1. Protected alpha-amino acid 1, which may be commerciallyavailable or readily prepared from the corresponding amino acid byprotection using, for example, di-tert-butyl dicarbonate (for P=BOC),carbobenzyloxy chloride (for P=Cbz), orN-(9-fluorenylmethoxycarbonyloxy)succinimide (for P=Fmoc), is treatedwith isobutyl chloroformate and a base such as triethylamine orN,N-diisopropylethylamine (DIEA), followed by diazomethane. Theresultant diazoketone is then treated with silver benzoate in a solventsuch as methanol or aqueous dioxane which may be subjected to sonicationfollowing the procedure of Sewald et al., Synthesis, 837 (1997) in orderto provide the beta amino acid II. As will be understood by thoseskilled in the art, for the preparation of enantiomerically pure betaamino acids II, enantiomerically pure alpha amino acids 1 may be used.Alternate routes to the protected beta-amino acid intermediates II canbe found in the following reviews: E. Juaristi, EnantioselectiveSynthesis of β-Amino Acids, Ed., Wiley-VCH, New York: 1997; Juaristi etal., Aldrichimica Acta, 27: 3 (1994); and Cole et al., Tetrahedron, 32:9517 (1994).

Compounds III are commercially available, known in the literature or maybe conveniently prepared by a variety of methods familiar to thoseskilled in the art. One convenient method for the preparation ofcompounds IIIa, wherein R¹¹, R¹² and R¹³ are hydrogen, is shown inScheme 2. Unsaturated derivative 3 is reduced, for example, by treatmentwith hydrogen gas and a catalyst such as palladium on carbon or platinumoxide in a solvent such as methanol or ethanol to provide Compound IIIa.

Intermediates 3, from Scheme 2, are themselves commercially available,known in the literature or may be conveniently prepared by a variety ofmethods familiar to those skilled in the art. One such method when X isCR² and R⁹ and R¹⁰ are H is illustrated in Scheme 3. Aminopyrazine 4 istreated with a 2-haloketone such as 2-bromoketone 5 in a solvent such asmethanol or ethanol to provide intermediate 7. Alternatively, for thepreparation of intermediate 7 where R² is H, 2-bromo-dimethylacetal 6and a catalytic amount of acid such as hydrochloric acid may be employedinstead of intermediate 5. The conversion of 4 to 7 may also be carriedout in two steps. First, 4 and an appropriate bromide 5 are heated,conveniently in a solvent such as dioxane at 50° C. for 16 h. Then,solvent is removed, the residue treated with isopropanol, and themixture heated at reflux for approximately 2 h. Intermediate 7 isconverted to 3a by treatment with a Grignard reagent in the presence ofcopper bromide according to the literature procedure detailed in J. Org.Chem., 52: 3847 (1987) or by palladium-catalyzed Suzuki coupling with aboronic acid.

Intermediates 3b, wherein X is CR² and R⁸ and R¹⁰ are H, may be preparedas described above for Scheme 3 starting with aminopyrazine 8A, asillustrated in Scheme 4.

Intermediates 3c, wherein X is CR² and R⁸ and R⁹ are H, may be preparedas described above for Scheme 3 starting with aminopyrazine 8B, asillustrated in Scheme 4A.

An alternate route for the preparation of Compound 3d wherein X is N andR⁹ and R¹⁰ are H is illustrated in Scheme 5. Dichloropyrazine 10 istreated with hydrazine to provide hydrazinochloropyrazine 11. Compound11 may be condensed with either an orthoester such as triethylorthoester 12 or with a carboxylic acid 13 in polyphosphoric acid (PPA)at elevated temperatures to give 14. Alternatively, the hydrazine 11 maybe acylated, for example, by treatment with an acid chloride oranhydride in the presence of a base such as triethylamine, and theresultant hydrazide cyclized to 14 by heating in polyphosphoric acid.Displacement of the halide using a Grignard reagent or Suzuki couplingas described above provides 3d.

Intermediates 3e, wherein X is N and R⁸ and R¹⁰ are H, may be preparedas described above for Scheme 5 starting with dichloropyrazine 15A, asillustrated in Scheme 6.

Intermediates 3f, wherein X is N and R⁸ and R⁹ are H, may be prepared asdescribed above for Scheme 5 starting with dichloropyrazine 15B, asillustrated in Scheme 6A.

Intermediates 3g, wherein X is N, may be prepared from chloropyrazine 18as illustrated in Scheme 7. Chloropyrazine 18, which is commerciallyavailable, known in the literature or may be conveniently prepared by avariety of methods familiar to those skilled in the art, is treated withhydrazine to provide hydrazinopyrazine 19, Intermediate 19 may becondensed with either an orthoester such as triethyl orthoester 12 orwith a carboxylic acid 13 in polyphosphoric acid at elevatedtemperatures to give 3g. Alternatively, the hydrazine 19 may beacylated, for example, by treatment with an acid chloride or anhydridein the presence of a base such as triethylamine, and the resultanthydrazide cyclized to 3g by heating in polyphosphoric acid.

Intermediates 3h, wherein X is CR², may also be prepared as illustratedin Scheme 8. Aminopyrazine 20, which is commercially available, known inthe literature or may be conveniently prepared by a variety of methodsfamiliar to those skilled in the art, is treated with a 2-haloketonesuch as 2-bromoketone 5 in a solvent such as methanol or ethanol toprovide intermediate 3h. Alternatively, for the preparation ofintermediate 3h where R² is H, 2-bromo-dimethylacetal 6 and a catalyticamount of acid such as hydrochloric acid may be employed instead ofintermediate 5. The conversion of 20 to 3h may also be carried out intwo steps. First, aminopyrazine 20 and an appropriate bromide 5 areheated, conveniently in a solvent such as dioxane at 50° C. for 16 h.Then, solvent is removed, the residue treated with isopropanol, and themixture heated at reflux for approximately 2 h to provide 3h.

An alternate method for the preparation of Intermediate IIIb, wherein Xis C—R² is illustrated in Scheme 9. Ring opening of epoxide 21, which iscommercially available, known in the literature or may be convenientlyprepared by a variety of methods familiar to those skilled in the art,with azide, conveniently using sodium azide in the presence of ammoniumchloride in DMF, gives azido alcohol 22. The alcohol is converted to thecorresponding triflate, and treated with an N-benzyl alpha-amino acidester, such as an ethyl ester, to provide amino ester 23. Aza-Wittigreaction affords iminoether 24. Treatment of 24 with 3-aminopropyneaccording to the procedure of Maffrand et al., Eur. J. Med. Chem., 10:528 (1975) gives tetrahydroimidazopyrazine 25, wherein R¹ is Me and R²is H, which may be deprotected using ammonium formate in the presence ofa palladium catalyst to give Intermediate IIIb. Alternatively,iminoether 24 may be converted to tetrahydroimidazopyrazine 25 bytreatment with an alpha-aminoketone, following procedures outlined inClaxton et al., J. Med. Chem., 17: 364 (1974).

An alternate route to the preparation of Intermediate IIIc, wherein X isN, is illustrated in Scheme 10. Iminoether 24, from Scheme 9, is treatedwith a hydrazide in, for example, ethanol at 60° C., followed by heatingin toluene at reflux, to give triazolopiperazine 26. Deprotection, forexample, using ammonium formate in the presence of a palladium catalyst,affords Intermediate IIIc.

Compounds III may be prepared from intermediate IIId, wherein R⁸ is H,as illustrated in Scheme 11. Intermediate IIId is protected with anitrogen protecting group, for example, a BOC group by treatment withdi-tert-butyldicarbonate. N-BOC derivative 27 is deprotonated withstrong base such as n-butyl lithium in the presence of TMEDA and treatedwith an alkylating agent such as an alkyl halide. Deprotection underacidic conditions provides compound III.

Compounds IIIe, wherein R⁸ and R¹¹ are hydrogen, may be prepared asshown in Scheme 12. Diamine 28 is treated with oxadiazole 29 in asolvent such as methanol, conveniently at 0° C. in the presence of abase such as N,N-diisopropylethylamine. Following removal of methanol,the intermediate mixture may be heated in superphosphoric acid toprovide the desired compounds IIIe.

Intermediates II and III are coupled under standard peptide couplingconditions, for example, using1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1-hydroxybenzotriazole(EDC/HOBT) or O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluroniumhexafluorophosphate and 1-hydroxy-7-azabenzotriazole (HATU/HOAT) in asolvent such as N,N-dimethylformamide (DMF) or dichloromethane for 3 to48 hours at ambient temperature to provide Intermediate 30 as shown inScheme 13. In some cases, Intermediate III may be a salt, such as ahydrochloride or trifluoroacetic acid salt, and in these cases it isconvenient to add a base, generally N,N-diisopropylethylamine, to thecoupling reaction. The protecting group is then removed with, forexample, trifluoroacetic acid or methanolic hydrogen chloride in thecase of Boc to give the desired amine I. The product is purified fromunwanted side products, if necessary, by recrystallization, trituration,preparative thin layer chromatography, flash chromatography on silicagel, such as with a Biotage® apparatus, or HPLC. Compounds that arepurified by HPLC may be isolated as the corresponding salt. Purificationof intermediates is achieved in the same manner.

In some cases the product I, prepared as described in Scheme 13, may befurther modified, for example, by manipulation of substituents on Ar,R¹, R², R⁸-R¹³. These manipulations may include, but are not limited to,reduction, oxidation, alkylation, acylation, and hydrolysis reactionsthat are commonly known to those skilled in the art.

In some cases intermediates described in the above schemes may befurther modified before the sequences are completed, for example, bymanipulation of substituents on Ar, R¹, R², R⁸-R¹³. These manipulationsmay include, but are not limited to, reduction, oxidation, alkylation,acylation, and hydrolysis reactions that are commonly known to thoseskilled in the art.

In some cases the order of carrying out the foregoing reaction schemesmay be varied to facilitate the reaction or to avoid unwanted reactionproducts. The following examples are provided so that the inventionmight be more fully understood. These examples are illustrative only andshould not be construed as limiting the invention in any way.

Intermediate 1

(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoic acidStep A: (R,S)—N-(tert-Butoxycarbonyl)-2,5-difluorophenylalanine

To a solution of 0.5 g (2.49 mmol) of 2,5-difluoro-DL-phenylalanine in 5mL of tert-butanol were added sequentially 1.5 mL of 2N aqueous sodiumhydroxide solution and 543 mg of di-tert-butyl dicarbonate. The reactionwas stirred at ambient temperature for 16 h and diluted with ethylacetate. The organic phase was washed sequentially with 1N hydrochloricacid and brine, dried over magnesium sulfate and concentrated in vacuo.The crude material was purified by flash chromatography (silica gel,97:2:1 dichloromethane:methanol:acetic acid) to afford the titlecompound. LC/MS 302 (M+1).

Step B:(R,S)-3-[(tert-Butoxycarbonyl)amino]-1-diazo-4-(2,5-difluoro-phenyl)butan-2-one

To a solution of 2.23 g (7.4 mmol) of(R,S)—N-(tert-butoxycarbonyl)-2,5-difluorophenylalanine in 100 mL ofdiethyl ether at 0° C. were added sequentially 1.37 mL (8.1 mmol) oftriethylamine and 0.931 mL (7.5 mmol) of isobutyl chloroformate and thereaction was stirred at this temperature for 15 min. A cooled etherealsolution of diazomethane was then added until the yellow color persistedand stirring was continued for a further 16 h. The excess diazomethanewas quenched by dropwise addition of acetic acid, and the reaction wasdiluted with ethyl acetate and washed sequentially with 5% hydrochloricacid, saturated aqueous sodium bicarbonate solution and brine, driedover magnesium sulfate and concentrated in vacuo. Purification by flashchromatography (silica gel, 4:1 hexane:ethyl acetate) afforded thediazoketone.

¹H NMR (500 MHz, CDCl₃): δ 7.03-6.95 (m, 1H), 6.95-6.88 (m, 2H), 5.43(bs, 1H), 5.18 (bs, 1H), 4.45 (bs, 1H), 3.19-3.12 (m, 1H), 2.97-2.80 (m,1H), 1.38 (s, 9H).

Step C:(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoic acid

To a solution of 2.14 g (6.58 mmol) of(R,S)-3-[(tert-butoxycarbonyl)-amino]-1-diazo-4-(2,5-difluorophenyl)butan-2-onedissolved in 100 mL of methanol at −30 ° C. were added sequentially 3.3mL (19 mmol) of N,N-diisopropylethylamine and 302 mg (1.32 mmol) ofsilver benzoate. The reaction was stirred for 90 min before dilutingwith ethyl acetate and washing sequentially with 2N hydrochloric acid,saturated aqueous sodium bicarbonate, and brine. The organic phase wasdried over magnesium sulfate, concentrated in vacuo and the enantiomerswere separated by preparative chiral HPLC (Chiralpak AD column, 5%ethanol in hexanes) to give the desired (R)-enantiomer, which elutedfirst. This material was dissolved in 50 mL of a mixture oftetrahydrofuran:methanol:1N aqueous lithium hydroxide (3:1:1) andstirred at 50° C. for 4 h. The reaction was cooled, acidified with 5%dilute hydrochloric acid and extracted with ethyl acetate. The combinedorganic phases were washed with brine, dried over magnesium sulfate andconcentrated in vacuo to give the title compound as a white foamy solid.

¹H NMR (500 MHz, CDCl₃): δ 7.21 (m, 1H), 6.98 (m, 2H), 6.10 (bs, 1H),5.05 (m,1H), 4.21 (m, 1H), 2.98 (m, 2H), 2.60 (m, 2H), 1.38 (s, 9H).

Intermediate 2

(3R)-3-[(tert-Butoxycarbonyl)amino]-4-[2-fluoro-4-(trifluoromethyl)phenyl]-butanoicacid Step A:(2R,5S)-2,5-Dihydro-3,6-dimethoxy-2-(2′-fluoro-4′-(trifluoromethyl)benzyl)-5-isopropylpyrazine

To a solution of 3.32 g (18 mmol) of commercially available(2S)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine in 100 mL oftetrahydrofuran at −70 ° C. was added 12 mL (19 mmol) of a 1.6M solutionof butyllithium in hexanes. After stirring at this temperature for 20min, 5 g (19.5 mmol) of 2-fluoro-4-trifluoromethylbenzyl bromide in 20mL of tetrahydrofuran was added and stirring was continued for 3 hbefore warming the reaction to ambient temperature. The reaction wasquenched with water, concentrated in vacuo, and extracted with ethylacetate. The combined organic phase was washed with brine, dried, andconcentrated in vacuo. Purification by flash chromatography (silica gel,0-5% ethyl acetate in hexanes) afforded the title compound.

¹H NMR (500 MHz, CDCl₃): δ 7.33-7.25 (m, 3H), 4.35-4.31 (m, 1H), 3.75(s, 3H), 3.65 (s, 3H), 3.60 (t, 1H, J=3.4 Hz), 3.33 (dd, 1H, J=4.6, 13.5Hz), 3.03 (dd, 1H, J=7, 13.5 Hz), 2.25-2.15 (m, 1H), 1.0 (d, 3H, J=7Hz), 0.66 (d, 3H, J=7 Hz).

Step B:(R)—N-(tert-Butoxycarbonyl)-2-fluoro-4-trifluoromethyl-phenylalaninemethyl ester

To a solution of 5.5 g (15 mmol) of(2R,5S)-2,5-dihydro-3,6-dimethoxy-2-(2′-fluoro-4′-(trifluoromethyl)benzyl)-5-isopropylpyrazinein 50 mL of a mixture of acetonitrile:dichloromethane (10:1) was added80 mL of 1N aqueous trifluoroacetic acid. The reaction was stirred for 6h and the organic solvents were removed in vacuo. Sodium carbonate wasadded until the solution was basic (>pH 8), and then the reaction wasdiluted with 100 mL of tetrahydrofuran and 10 g (46 mmol) ofdi-tert-butyl dicarbonate was added. The resulting slurry was stirredfor 16 h, concentrated in vacuo, and extracted with ethyl acetate. Thecombined organic phase was washed with brine, dried, and concentrated invacuo. Purification by flash chromatography (silica gel, 20% ethylacetate in hexanes) afforded the title compound.

¹H NMR (500 MHz, CDCl₃): δ 7.38-7.28 (m, 3H), 5.10 (bd, 1H), 4.65-3.98(m, 1H), 3.76 (s, 3H), 3.32-3.25 (m, 1H), 3.13-3.05 (m, 1H), 1.40 (s,9H).

Step C:(R)—N-(tert-Butoxycarbonyl)-2-fluoro-4-(trifluoromethyl)phenylalanine

A solution of 5.1 g (14 mmol) of(R,S)—N-(tert-butoxycarbonyl)-2-fluoro-4-(trifluoromethyl)phenylalaninemethyl ester in 350 mL of a mixture of tetrahydrofuran:methanol:1Nlithium hydroxide (3:1:1) was stirred at 50° C. for 4 h. The reactionwas cooled, acidified with 5% hydrochloric acid and extracted with ethylacetate. The combined organic phases were washed with brine, dried overmagnesium sulfate and concentrated in vacuo to give the title compound.

¹H NMR (500 MHz, CD₃OD): δ 7.45-7.38 (m, 3H), 4.44-4.40 (m, 1H),3.38-3.33 (m, 1H), 2.98 (dd, 1H, J=9.6, 13.5 Hz), 1.44 (s, 9H).

Step D:(3R)-3-[(tert-Butoxycarbonyl)amino]-4-[2-fluoro-4-(trifluoromethyl)-phenyl]-butanoicacid

To a solution of 3.4 g (9.7 mmol) of the product from Step C in 60 mL oftetrahydrofuran at 0° C. were added sequentially 2.3 mL (13 mmol) ofN,N-diisopropylethylamine and 1.7 mL (13 mmol) of isobutyl chloroformateand the reaction was stirred at this temperature for 30 min. A cooledethereal solution of diazomethane was then added until the yellow colorpersisted and stirring was continued for a further 16 h. The excessdiazomethane was quenched by dropwise addition of acetic acid, and thereaction was diluted with ethyl acetate and washed sequentially with 5%hydrochloric acid, saturated aqueous sodium bicarbonate solution andbrine, dried over magnesium sulfate and concentrated in vacuo.Purification by flash chromatography (silica gel, 9:1 hexane:ethylacetate) afforded 0.5 g of diazoketone. To a solution of 0.5 g (1.33mmol) of the diazoketone dissolved in 100 mL of methanol at 0° C. wereadded sequentially 0.7 mL (4 mmol) of N,N-diisopropylethylamine and 32mg (0.13 mmol) of silver benzoate. The reaction was stirred for 2 hbefore diluting with ethyl acetate and washing sequentially with 2Nhydrochloric acid, saturated aqueous sodium bicarbonate, and brine. Theorganic phase was dried over magnesium sulfate, concentrated in vacuoand dissolved in 50 mL of a mixture of tetrahydrofuran:methanol:1Naqueous lithium hydroxide (3:1:1) and stirred at 50° C. for 3 h. Thereaction was cooled, acidified with 5% hydrochloric acid and extractedwith ethyl acetate. The combined organic phases were washed with brine,dried over magnesium sulfate and concentrated in vacuo to give the titlecompound as a white foamy solid.

¹H NMR (500 MHz, CD₃OD): δ 7.47-7.33 (m, 3H), 4.88 (bs, 1H), 4.26-3.98(m, 1H), 3.06-3.01 (m, 1H), 2.83-2.77 (m, 1H), 2.58-2.50 (m, 2H), 1.29(s, 9H).

Intermediate 3

(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid Step A: (2S,5R)-2,5-Dihydro-3,6-dimethoxy-2-isopropyl-5-(2′,4′,5′trifluorobenzyl)-pyrazine

The title compound (3.81 g) was prepared from 3.42 g (18.5 mmol) of(2S)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine and 5 g (22.3 mmol)of 2,4,5-trifluorobenzyl bromide using the procedure described forIntermediate 2, Step A.

¹H NMR (500 MD, CDCl₃): δ 7.01 (m, 1H), 6.85 (m, 1H), 4.22 (m, 1H), 3.78(m, 3H), 3.64 (m, 3H), 3.61 (m, 1H), 3.20 (m, 1H), 2.98 (m, 1H), 2.20(m, 1H), 0.99 (d, 3H, J=8 Hz), 0.62 (d, 3H, J=8 Hz).

Step B: (R)—N-(tert-Butoxycarbonyl)-2,4,5-trifluorophenylalanine methylester

To a solution of 3.81 g (11.6 mmol) of(2S,5R)-2,5-dihydro-3,6-dimethoxy-2-isopropyl-5-(2′,4′,5′trifluorobenzyl)pyrazinein 20 mL of acetonitrile was added 20 mL of 2N hydrochloric acid. Thereaction was stirred for 72 h and concentrated in vacuo. The residue wasdissolved in 30 mL of dichloromethane and 10 mL (72 mmol) oftriethylamine and 9.68 g (44.8 mmol) of di-tert-butyl dicarbonate wereadded. The reaction was stirred for 16 h, diluted with ethyl acetate andwashed sequentially with 1N hydrochloric acid and brine. The organicphase was dried over sodium sulfate, concentrated in vacuo and purifiedby flash chromatography (silica gel, 9:1 hexanes:ethyl acetate) toafford the title compound.

¹H NMR (500 MHz, CDCl₃): δ 6.99 (m, 1H), 6.94 (m, 1H), 5.08 (m, 1H),4.58 (m, 1H), 3.78 (m, 3H), 3.19 (m, 1H), 3.01 (m, 1H), 1.41 (s, 9H).

Step C: (R)—N-(tert-Butoxycarbonyl)-2,4,5-trifluorophenylalanine

The title compound was prepared from 2.41 g (7.5 mmol) of(R)—N-(tert-butoxycarbonyl)-2,4,5-trifluorophenylalanine methyl esterusing the procedure described for Intermediate 2, Step C.

LC-MS 220.9 (M+1-BOC).

Step D:(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)-butanoicacid

To a solution of 0.37 g (1.16 mmol) of(R)—N-(tert-butoxycarbonyl)-2,4,5-trifluorophenylalanine in 10 mL ofdiethyl ether at −20° C. were added sequentially 0.193 mL (1.3 mmol) oftriethylamine and 0.18 mL (1.3 mmol) of isobutyl chloroformate, and thereaction was stirred at this temperature for 15 min. A cooled etherealsolution of diazomethane was then added until the yellow color persistedand stirring was continued for a further 1 h. The excess diazomethanewas quenched by dropwise addition of acetic acid, and the reaction wasdiluted with ethyl acetate and washed sequentially with saturatedaqueous sodium bicarbonate solution and brine, dried over magnesiumsulfate and concentrated in vacuo. Purification by flash chromatography(silica gel, 3:1 hexane:ethyl acetate) afforded 0.36 g of diazoketone.To a solution of 0.35 g (1.15 mmol) of the diazoketone dissolved in 12mL of 1,4-dioxane:water (5:1) was added 26 mg (0.113 mmol) of silverbenzoate. The resultant solution was sonicated for 2 h before dilutingwith ethyl acetate and washing sequentially with 1N hydrochloric acidand brine, drying over magnesium sulfate and concentrating in vacuo.Purification by flash chromatography (silica gel, 97:2:1dichloromethane:methanol:acetic acid) afforded the title compound.

¹H NMR (500 MHz, CDCl₃): δ 7.06 (m, 1H), 6.95 (m, 1H), 5.06 (bs, 1H),4.18 (m, 1H), 2.98 (m, 2H), 2.61 (m, 2H), 1.39 (s, 9H).

Intermediate 4

(3R)-4-(2-Bromo-4,5-difluorophenyl)-3-[(tert-butoxycarbonyl)amino]-butanoicacid

To a solution of 2.4 g (10 mmol) of 2-bromo-4,5-difluorobenzoic acid[prepared according to the procedure of Braish et al., Syn. Comm.,3067-3074 (1992)] in 75 mL of tetrahydrofuran was added 2.43 g (15 mmol)of 1,1′-carbonyldiimidazole. The solution was heated under reflux for3.5 h, cooled to ambient temperature and 0.38 g (10 mmol) of sodiumborohydride in 15 mL of water was added. The reaction was stirred for 10min and partitioned between ethyl acetate and 10% aqueous sodiumbicarbonate solution. The organic layer was washed twice with warmwater, brine, dried over magnesium sulfate, and concentrated in vacuo.Purification by flash chromatography (silica gel, 4:1 hexane:ethylacetate) afforded 1.9 g of 2-bromo-4,5-difluorobenzyl alcohol. To asolution of 1.9 g (8.4 mmol) of 2-bromo-4,5-difluorobenzyl alcohol in 30mL of dichloromethane at 0° C. was added 3.4 g (10 mmol) of carbontetrabromide and 2.7 g (10 mmol) of triphenylphosphine. The reaction wasstirred for 2 h at this temperature, the solvent was removed in vacuoand the residue stirred with 100 mL of diethyl ether. The solution wasfiltered, concentrated in vacuo, and purified by flash chromatography(silica gel, 20:1 hexane:ethyl acetate) to afford 2.9 g of2-bromo-4,5-difluorobenzyl bromide contaminated with carbon tetrabromidewhich was used without further purification. Using the proceduresoutlined for the preparation of Intermediates 1-3, the benzyl bromidederivative was converted to the title compound.

LC/MS 394 and 396 (M+1).

Essentially following the procedures outlined for the preparation ofIntermediates 1-4, the Intermediates in Table 1 were prepared. TABLE 1

Inter- mediate R³ Selected ¹H NMR data (CD₃OD) 5 2-F,4-Cl,5-F 7.11 (dd,1H, J=8.9, 6.4Hz), 7.03 (dd, 1H, J=9.0, 6.6) 6 2-F,5-Cl 7.27 (dd, 1H,J=6.4, 2.5Hz), 7.21 (m, 1H), 7.03 (t, 1H, J=9.2Hz) 7 2-Me,5-Cl 7.16 (d,1H, J=1.8Hz), 7.11-7.07 (m, 2H), 2.34 (s, 3H) 8 2-Cl,5-Cl 7.34 (d, 1H,J=9.0), 7.33 (d, 1H, J=2.1 Hz), 7.21 (dd, 1H, J=8.5, 2.5Hz) 92-F,3-Cl,6-F 7.35 (td, 1H, J=8.5, 5.8Hz), 6.95 (t, 1H, J=8.5Hz) 103-Cl,4-F 7.33 (d, 1H, J=6.9Hz), 7.19-7.11 (m, 2H) 11 2-F,3-F,6-F7.18-7.12 (m, 1H), 6.91 (m, 1H) 12 2-F,4-F,6-F 6.81 (t, 2H, J=8.4Hz) 132-OCH₂Ph,5-F 7.49 (d, 2H, J=7.6Hz), 7.38 (t, 2H, J= 7.3Hz), 7.30 (t, 1H,J=7.3Hz), 6.96- 6.89 (m, 3H), 5.11 (d, 1H, J=11.7Hz), 5.08 (d, 1H,J=11.9Hz)

EXAMPLE 1

Ethyl7-[(3R)-3-amino-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid, trifluoroacetic acid salt Step A: Ethylimidazo[1,2-a]pyrazine-2-carboxylate

To a solution of 2-aminopyrazine (1.0 g, 10.5 mmol) in dioxane (25 mL)was added ethyl 3-bromo-2-ketopropionate (2.0 g, 10.5 mmol). Thereaction was stirred at 50° C. for 16 h. The mixture was filtered andthe solid was washed with two portions of ethyl acetate. The solid washeated in 35 mL of isopropanol at reflux temperature for 4 h. Thereaction mixture was concentrated and partitioned between ethyl acetateand saturated aqueous sodium bicarbonate. The aqueous phase wasextracted with three portions of ethyl acetate. The combined organicswere washed with brine, dried over magnesium sulfate, and concentrated.Purification by chromatography (Biotage system, silica gel, ethylacetate then 10% methanol/ethyl acetate) gave the title compound as asolid.

Step B: Ethel 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

A mixture of 1.9 g of ethyl imidazo[1,2-a]pyrazine-2-carboxylate (StepA) and 280 mg of 10% palladium on carbon was stirred under an atmosphereof hydrogen overnight. The mixture was filtered through a pad of Celiteand the filtrate concentrated. Purification by flash chromatography on aBiotage® system (silica gel, eluting with 50% ethyl acetate/hexane,ethyl acetate, 10% methanol/ethyl acetate and 80:15:1chloroform/methanol/ammonium hydroxide) gave the title compound.

Step C: Ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

To a solution of 150 mg (0.768 mmol) of ethyl5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate (Step B) and 242mg (0.768 mmol) of(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoic acid(Intermediate 1) in 65 mL of DMF was added 125 mg (0.922 mmol) of HOBTand 177 mg (0.922 mmol) of EDC. The resultant mixture was stirred atambient temperature for 14 h, and then partitioned between ethyl acetateand saturated aqueous sodium bicarbonate solution. The aqueous phase wasextracted with three portions of ethyl acetate. The combined organicphases were washed with brine, dried over magnesium sulfate, andconcentrated. Purification by flash chromatography on a Biotage® system(silica gel, eluting with 50% ethyl acetate/hexane, ethyl acetate, and10% methanol/ethyl acetate) gave the title compound.

Step D: Ethyl7-[(3R)-3-amino-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-α]pyrazine-2-carboxylate,trifluoroacetic acid salt

To a solution of 28 mg of ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylatein 0.5 mL of dichloromethane was added 0.5 mL of trifluoroacetic acid.The reaction mixture was stirred at ambient temperature for 1.5 h.Concentration gave the title compound as a solid. LC/MS 393 (M+1).

EXAMPLE 2

7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid, trifluoroacetic acid salt

To a solution of 165 mg (0.335 mmol) of ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]4-(2,5-difluorophenyl)butanoyl2-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate(Example 1, Step C) in 2 mL of tetrahydrofuran and 2 mL of water wasadded lithium hydroxide (24 mg, 1.01 mmol). The reaction mixture wasstirred at ambient temperature for 14 h. It was then concentrated andpartitioned between ethyl acetate and 2N aqueous hydrochloric acid. Theaqueous phase was washed sequentially with three portions of ethylacetate. Concentration of the aqueous phase provided the title compound,which was purified by HPLC (YMC Pro-C18 column, gradient elution, 5-95%acetonitrile/water with 0.1% TFA) to give the title compound. LCIMS 365(M+1).

EXAMPLE 3

7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-N,N-dimethyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide,dihydrochloride Step A:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid

To a solution of 295 mg (0.6 mmol) of ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate(Example 1, Step C) in 4 mL of tetrahydrofuran and 4 mL of water wasadded 57.7 mg (2.4 mmol) of lithium hydroxide. The mixture was stirredat ambient temperature for 14 h. It was then concentrated to a volume ofapproximately 4 mL. Acetic acid (0.173 mL) was added and the mixture wasextracted sequentially with three portions of ethyl acetate. Thecombined organic phase was washed with brine, dried over magnesiumsulfate, and concentrated to provide the title compound as a whitesolid.

Step B:N,N-Dimethyl-7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-α]pyrazine-2-carboxamide

To a solution of 50 mg (0.108 mmol) of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid (Step A) and 0.108 mL of a 2M solution of dimethylamine intetrahydrofuran in 1 mL of DMF was added 17.5 mg (0.13 mmol) of HOBT and24.9 mg (0.13 mmol) of EDC. The reaction mixture was stirred at ambienttemperature for 18 h and then concentrated. Purification bychromatography (Biotage system, silica gel, eluting sequentially withethyl acetate, 10% methanol/ethyl acetate, and 10%methanol/dichloromethane) provided the title compound as a white solid.

Step C:7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-N,N-dimethyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide,dihydrochloride

A solution of 22 mg ofN,N-dimethyl-7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide(Step B) in saturated methanolic hydrogen chloride was stirred atambient temperature for 1 h. Concentration gave the title compound as awhite solid. LC/MS 392 (M+1).

EXAMPLE 4

7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide,trifluoroacetic acid salt Step A:7-[(3R)-3-[(tert-Butoxcarbonyl)amino]-4(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide

A solution of 100 mg of ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate(Example 1, Step C) in 3.5 mL of concentrated ammonium hydroxide washeated in a sealed tube at 100° C. for 6 h. The reaction mixture wasconcentrated in vacuo and purified by chromatography (Biotage system,silica gel, 10% methanol/ethyl acetate) to give the title compound.

Step B:7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide,trifluoroacetic acid salt

To a solution of 26 mg of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxamide(Step A) in 0.4 mL of dichloromethane was added 0.4 mL oftrifluoroacetic acid. The reaction mixture was stirred at ambienttemperature for 1 h and then concentrated to provide the title compoundas a foamy solid.

EXAMPLE 5

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-2-(trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,trifluoroacetic acid salt Step A:4-Methyl-N-[(2E)-pyrazine-2(1H)-ylidene]benzenesulfonamide

To a solution of 2-aminopyrazine (5.00 g, 52.5 mmol) in pyridine (40 mL)was added p-toluenesulfonyl chloride (11.0 g, 57.8 mmol). The reactionwas stirred at ambient temperature for 80 min. After the pyridine wasevaporated under vacuum, 0.5 L of water was added and the mixture wasstirred at ambient temperature for 1 h. The reaction was filtered andthe solid was washed sequentially with one portion of water and twoportions of diethyl ether. The solid was dried under vacuum to give thetitle compound which was directly used in the next step without furtherpurification. LC/MS 250 (M+1).

Step B:2-[(2E)-2-[[(4-Methylphenyl)sulfonyl]imino]pyrazin-1(2H)-yl]acetamide

To a suspension of 4.50 g (18.1 mmol) of4-methyl-N-[(2E)-pyrazine-2(1H)-ylidene]benzenesulfonamide (Step A) in30 mL of N,N-dimethylformamide was added 3.46 mL (19.9 mmol) ofdiisopropylethylamine and 3.67 g (19.9 mmol) of iodoacetamide. After thereaction was stirred at ambient temperature for 28 h, the mixture waspoured into 20 mL of water and stirred for 100 min. The reaction mixturewas filtered and the solid was washed sequentially with 200 mL of waterand 100 mL of diethyl ether to afford the title compound as a solid.

Step C: 2,2,2-Trifluoro-N-imidazo[1,2-a]pyrazin-2-ylacetamide

To a solution of 1.0 g (3.26 mmol) of2-[(2E)-2-[[(4-methylphenyl)sulfonyl]imino]pyrazin-1(2H)-yl]acetamide(Step B) in 15 mL of dichloromethane was added 6 mL of trifluoroaceticanhydride. After the reaction was refluxed for 6 h, the solvent wasevaporated and 30 mL of ethyl acetate was added. The mixture wasfiltered and the solid was washed with ethyl acetate to give the titlecompound as a solid. ¹H NMR (500 MHz, DMSO-d₆): δ 9.13 (s, 1H), 8.62 (d,1H), 8.38 (s, 1H), 8.08 (d, 1H.).

Step D:2,2,2-Trifluoro-N-(5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl)acetamide

The title compound was prepared from2,2,2-trifluoro-N-imidazo[1,2-a]pyrazin-2-ylacetamide (Step C) using aprocedure analogous to that of Example 1, Step B.

Step E:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl-2-(trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from2,2,2-trifluoro-N-(5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl)acetamide(Step D) and(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) using a procedure analogous to that of Example 1,Step C. LC/MS 550 (M+1).

Step F:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-2-(trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,trifluoroacetic acid salt

The title compound was prepared from7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-2-(trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(from Step E) using a procedure analogous to that of Example 1, Step D.LC/MS 450 (M+1).

EXAMPLE 6

3-Amino-7-[(3R)-3-amino-4-(2,4,5-difluorophenyl)butanoyl]-2-cyclopropyl-5,6,7,8-tetrahydroimidazo]1,2-a]pyrazine,trifluoroacetic acid salt Step A:2-Cyclopropyl-N-(1-isopropyl-3,3-dimethylbutyl)imidazo[1,2-a]pyrazin-3-amine

To a solution of 2-aminopyrazine (1.13 g, 11.9 mmol) in methanol (12 mL)and dichloromethane (12 mL) was added 1,1,3,3-tetramethylbutylisocyanide (2.50 mL, 14.3 mmol), cyclopropanecarboxaldehyde (1.00 g,14.3 mmol) and scandium triflate (292 mg, 0.595 mmol). The reaction wasstirred at ambient temperature for 24 h. The reaction mixture wasconcentrated under vacuum and purified by flash chromatography (silicagel, 100% dichloromethane then 10% methanol in dichloromethane) toafford the title compound as a solid. LC/MS 287 (M+1).

Step B:2-Cyclopropyl-N-(1,1,3,3-tetramethylbutyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-3-amine

The title compound was prepared from2-cyclopropyl-N-(1-isopropyl-3,3-dimethylbutyl)imidazo[1,2-a]pyrazin-3-amine(Step A) using a procedure analogous to that of Example 1, Step B. LC/MS291 (M+1).

Step C:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-3-[(1,1,3,3-tetramethylbutyl)amino]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from2-cyclopropyl-N-(1,1,3,3-tetramethylbutyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-3-amine(Step B) and(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) using a procedure analogous to that of Example 1,Step C. LC/MS 606 (M+1).

Step D:3-Amino-7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,trifluoroacetic acid salt

To a solution of 35.0 mg of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-3-[(1,1,3,3-tetramethylbutyl)amino]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step C) in 1 mL of dichloromethane was added 1 mL of trifluoroaceticacid. The reaction was stirred at ambient temperature for 1 h. Themixture was concentrated and purified by reverse-phase HPLC (YMC Pro-C18column, gradient elution, 10-30% acetonitrile/water with 0.1% TFA) togive the title compound as a solid. LC/MS 394 (M+1).

EXAMPLE 7

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-3-(2,2,2-trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,trifluoroacetic acid salt Step A:2-Cyclopropylimidazo[1,2-a]pyrazin-3-amine

To a solution of 1.50 g (8.06 mmol) of2-cyclopropyl-N-(1-isopropyl-3,3-dimethylbutyl)imidazo[1,2-a]pyrazin-3-amine(Example 6, Step A) in 4 mL of dichloromethane was added 4 mL oftrifluoroacetic acid and the reaction was stirred at ambient temperaturefor 1 h. The mixture was concentrated in vacuo to give the titlecompound as a viscous oil. LC/MS 175 (M+1).

Step B:N-(2-Cyclopropylimidazo[1,2-a]pyrazin-3-yl)-2,2,2-trifluoroacetamide

To a solution of 350 mg (1.22 mmol) of2-cyclopropylimidazo[1,2-a]pyrazin-3-amine (Step A) in 5 mL ofdichloromethane at 0° C. was added pyridine (0.628 mL, 7.29 mmol) andtrifluoroacetic anhydride (0.513 mL, 3.65 mmol). The reaction wasstirred at 0° C. for 1 h. After the mixture was concentrated at 0° C.under vacuum, 1 mL of ice-cold water was added. The reaction mixture wasthen purified by reverse-phase HPLC (YMC Pro-C18 column, gradientelution, 10-90% acetonitrile/water with 0.1% TFA) to afford the titlecompound as a solid. LC/MS 271 (M+1).

Step C:N-(2-Cyclopropyl-5,6,7,8-tetrahydroimidazo]1,2-a]pyrazin-3-yl)-2,2,2-trifluoroacetamide

The title compound was prepared fromN-(2-cyclopropylimidazo[1,2-a]pyrazin-3-yl)-2,2,2-trifluoroacetamide(Step B) using a procedure analogous to that of Example 1, Step B.

Step D:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-3-(2,2,2-trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo]1,2-a]pyrazine

The title compound was prepared fromN-(2-cyclopropyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-3-yl)-2,2,2-trifluoroacetamide(Step C) and(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) using a procedure analogous to that of Example 1,Step C. LC/MS 590 (M+1).

Step E:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-3-(2,2,2-trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,trifluoroacetic acid salt

The title compound was prepared from7-[(3R)-3-[(tert-butoxylcarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-2-cyclopropyl-3-(2,2,2-trifluoroacetylamino)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(fromStep D) using a procedure analogous to that of Example 1, Step D. LC/MS490 (M+1).

EXAMPLE 8

Ethyl7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl-5,6,7,8-tetrahydro1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate,hydrochloride Step A: Ethyl oxo(2-pyrazin-2-ylhydrazino)acetate

To a mixture of 2.38 g (21.6 mmol) of 2-hydrazinopyrazine and 2.41 g(3.32 mL, 23.8 mmol) of triethylamine in 50 mL of acetonitrile was added3.25 g (2.66 mL, 23.8 mmol) of ethyl chloro(oxo)acetate at 0° C. Thereaction mixture was stirred at ambient temperature for 18 h, and thenpartitioned between aqueous sodium bicarbonate solution and ethylacetate. The aqueous phase was extracted with three portions of ethylacetate. The combined organic phases were washed with brine, dried overmagnesium sulfate, and concentrated to give the title compound. LC/MS211 (M+1).

Step B: Ethyl [1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate

To a solution of 521 mg (2.48 mmol) of ethyloxo(2-pyrazin-2-ylhydrazino)acetate from Step A in 10 mL of toluene wasadded 20 mg of p-toluenesulfonic acid. The mixture was heated at refluxfor 18 h. The reaction mixture was washed with aqueous sodiumbicarbonate solution. The aqueous phase was extracted with threeportions of ethyl acetate. The combined organic phases were washed withbrine, dried over magnesium sulfate, and concentrated to give the titlecompound. LC/MS 192.9 (M+1).

Step C: Ethel5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate

A mixture of 380 mg of ethyl[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate from Step B and 50 mg of10% palladium on carbon in 10 mL of ethyl acetate and 10 mL of ethanolwas stirred under an atmosphere of hydrogen for 18 h. The mixture wasfiltered through a pad of Celite and the filtrate concentrated to givethe title compound as a solid. LC/MS 169 (M+1).

Step D: Ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate

A 264 mg (1.35 mmol) portion of ethyl5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate from StepC was coupled to(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) essentially following the procedure outlined inExample 1, Step C. Purification by flash chromatography on a Biotage®system (silica gel, eluting with 5% methanol/dichloromethane) gave thetitle compound. LC/MS 456 (M+1-tBu).

Step E: Ethyl7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate,hydrochloride

A 10 mg portion of ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylatefrom Step D was deprotected essentially following the procedure outlinedin Example 3, Step C to provide the title compound. LC/MS 412 (M+1).

EXAMPLE 9

N-(tert-Butyl)-7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydro1,2,4]triazolo[4,3-a]pyrazine-3-carboxamide,hydrochloride Step A:N-(tert-Butyl)[1,2,4]triazolo[4,3-a]pyrazine-3-carboxamide

A mixture of 170 mg of ethyl[1,2,4]triazolo[4,3-a]pyrazine-3-carboxylate from Example 8, Step B and3 mL of tert-butylamine was heated in a sealed tube at reflux for 8 h.Concentration followed by flash chromatography (silica gel, elutingsequentially with 100% ethyl acetate and 10% methanol/dichloromethane)gave the title compound as a viscous oil. LC/MS 219.9 (M+1).

Step B:N-(tert-Butyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxamide

A mixture from 167 mg ofN-(tert-butyl)[1,2,4]triazolo[4,3-a]pyrazine-3-carboxamide from Step Aand 20 mg of 10% palladium on carbon in 3 mL of ethanol was stirredunder an atmosphere of hydrogen for 18 h. The mixture was filteredthrough a pad of Celite and the filtrate concentrated to give the titlecompound as a solid. ¹H NMR (CDCl₃): δ 7.22 (1H, s), 4.43 (2H, t, J=5.5Hz), 4.32 (2H, s), 3.27 (2H, t, J=5.5 Hz), 2.05 (1H, br), 1.48 (9H, s).

Step C:N-(tert-Butyl)-7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydro]1,2,4]triazolo[4,3-a]pyrazine-3-carboxamide

A 32 mg (0.14 mmol) portion ofN-(tert-butyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxamidefrom Step B was coupled to(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) essentially following the procedure outlined inExample 1, Step C. Purification by preparative TLC (silica gel, 10%methanol/dichloromethane) gave the title compound. LC/MS 483.1(M+1-tBu).

Step D:N-(tert-Butyl)-7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanol]-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxamide,hydrochloride

A 63 mg portion ofN-(tert-butyl)-7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine-3-carboxamidefrom Step C was deprotected essentially following the procedure outlinedin Example 3, Step C to provide the title compound. LC/MS 439 (M+1).

EXAMPLE 10

Ethyl7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate,trifluoroacetic acid salt Step A: Ethyl7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

To ethyl 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate (Example1, Step B, 23.8 g, 122 mmol) in 400 mL of dichloromethane was addeddi-tert-butyl dicarbonate (29.3 g, 134 mmol). The reaction mixture wasstirred at ambient temperature for 2 h then concentrated in vacuo.Purification by flash chromatography (silica gel, gradient elution, 70%ethyl acetate/hexane to 100% ethyl acetate to 10% methanol/ethylacetate) afforded the title compound.

Step B: Ethel7-(tert-butoxycarbonyl)-3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

To a solution of ethyl7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate(4.28 g, 14.5 mmol) from Step A in 100 mL of carbon tetrachloride wasadded N-chlorosuccinimide (2.325 g, 17.4 mmol) and benzoyl peroxide (50mg, 0.2 mmol) sequentially. The reaction was stirred at reflux for 1 h.The reaction mixture was cooled to 0° C., filtered, and the solid waswashed with two 25-mL portions of dichloromethane. The solvent wasconcentrated in vacuo. Purification by flash chromatography on aBiotage® system (silica gel, gradient, 50% ethyl acetate/hexane to 100%ethyl acetate) afforded the title compound.

Step C: Ethyl3-chloro-5,6,7,8-tetrahydroimidazo]1,2-a]pyrazine-2-carboxylate,trifluoroacetic acid salt

To a solution of 180 mg of ethyl7-(tert-butoxycarbonyl)-3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylatefrom Step B in 5 mL of dichloromethane was added 5 mL of trifluoroaceticacid. The reaction mixture was stirred at ambient temperature for 1.5 h.Concentration gave the title compound.

Step D: Ethyl7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

To a solution of ethyl3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate,trifluoroacetic acid salt (185 mg, 0.54 mmol) with(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (95 mg, 0.30 mmol) and N,N-diisopropylethylamine (DIEA) (0.188 mL,1.1 mmol) in 8 mL of dichloromethane was added HOAT (41 mg, 0.30 mmol)and HATU (113 mg, 0.30 mmol). The reaction mixture was stirred atambient temperature for 12 h. The reaction mixture was filtered though aplug of PSA resin (200 mg; Varian MEGA BOND ELUT, PSA) and the resinwashed with 10 mL of a 10% methanol/dichloromethane solution. Thefiltrate was concentrated in vacuo. Purification by reverse phase HPLC(YMC Pro-C18 column, gradient elution, 10-90% acetonitrile/water with0.1% TFA) afforded title compound as a white foam.

Step E: Ethyl7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate,trifluoroacetic acid salt

To a solution of ethyl7-[(3R)-3-[(tert-butoxylcarbonyl)amino]4-(2,4,5-trifluorophenyl)butanoyl]-3-chloro-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate(67 mg, 0.012 mmol) in 1 mL of dichloromethane was added 1 mL oftrifluoroacetic acid. The reaction mixture was stirred at ambienttemperature for 0.5 h and concentrated in vacuo. Purification by HPLC(YMC Pro-C18 column, gradient elution, 10-90% acetonitrile/water with0.1% TFA) provided the title compound as a white foam. MS 445.2 (M+1).

EXAMPLE 11

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-[(R orS)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid, trifluoroacetic acid salt and7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-[(S orR)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid, trifluoroacetic acid salt Step A: Ethyl3-bromo-7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

To a chloroform solution (250 mL) of ethyl7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylatefrom Example 10, Step A (18.4 g, 94 mmol), bromine (45 g, 281 mmol) wasadded, and the mixture was stirred at room temperature for an hour. Anaqueous solution of sodium bisulfite was then added and the product wasextracted with two 100-mL portions of dichloromethane. The combinedorganic extracts were washed sequentially with sodium bicarbonate andbrine, then dried over sodium sulfate and concentrated in vacuo. Thecrude material was purified by flash chromatography (silica gel,gradient elution, 50% ethyl acetate/hexane to 100% ethyl acetate) togive the title compound.

Step B: Ethyl7-(tert-butoxycarbonyl)-3-(1-ethoxyvinyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

The bromide from Step A (8.0 g, 21 mmol), tributyl(1-ethoxyvinyl)tin(8.7 mL, 26 mmol), tris(dibenzylideneacetone)dipalladium (0.98 g, 1.1mmol) and tri-2-furylphosphine (0.99 g, 4.3 mmol) were stirred indioxane (200 ml) under nitrogen at 110° C. for 6 h. After cooling toroom temperature, 200 mL of an aqueous solution of potassium fluoride(3.0 g) was added and the resulting mixture was extracted with three200-mL portions of ethyl acetate. The combined organic extracts werewashed sequentially with water and brine, then dried over sodiumsulfate, filtered, and concentrated. The crude material was purified byflash chromatography (silica gel, 50% ethyl acetate/hexane to 100% ethylacetate) to obtain the title compound.

Step C: Ethyl3-acetyl-7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

To the enol ether from Step B (5.78 g, 15.8 mmol) in 200 mL of a 10:1mixture of THF/water, para-toluenesulfonic acid (300 mg) was added. Thereaction mixture was heated at 50° C. for 2 hours. The reaction mixturewas then cooled to room temperature, concentrated in vacuo, and treatedwith 400 mL of ethyl acetate. The organic solution was washedsequentially with two 400-mL portions of aqueous saturated sodiumbicarbonate and one 400-mL portion of brine, dried over sodium sulfate,filtered, and concentrated in vacuo to give the title compound which wasused without further purification.

Step D: Ethyl7-(tert-butoxycarbonyl)-3-(1-hydroxyethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate

The ketone from Step C (5.6 g, 17 mmol) was dissolved in 200 mL ofmethanol and the solution was cooled to 0° C. Sodium borohydride (6.3 g,166 mmol) was added portionwise and the reaction mixture was allowed tostir at room temperature for 1 h. The reaction mixture was thenconcentrated in vacuo and treated with 400 mL of ethyl acetate, washedonce with brine (400 mL), dried over sodium sulfate, filtered, andconcentrated. Purification by flash chromatography on a Biotage® system(silica gel, gradient elution, 70% ethyl acetate/hexane to 100% ethylacetate) afforded the title compound as a racemic mixture. The racematewas resolved by chiral HPLC (ChiralCel OD (4.6×250 mm) 10 micron column,15% ethanol/hexane) to give the two enantiomers.

Step E: 7-(tert-Butoxycarbonyl)-3-[(R orS)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid

The faster eluting enantiomer (Enantiomer A) from Step D (223 mg, 0.65mmol) in 15 mL of a 3:1:1 mixture of tetrahydrofuran:methanol:1N aqueouslithium hydroxide solution was stirred at ambient temperature for 4 h.The THF was evaporated under reduced pressure. The reaction mixtureacidified with 5% hydrochloric acid, then extracted with ethyl acetate(3×30 mL). The combined organic phases were washed with brine, driedover magnesium sulfate and concentrated in vacuo. Purification by HPLC(YMC Pro-C18 column, gradient elution, 10-90% acetonitrile/water with0.1% TFA) afforded the title compound.

The same procedure was used to obtain the acid of the slower elutingenantiomer (Enantiomer B) from Step D.

Step F:6-(tert-Butoxycarbonyl)-1-methyl-5,6,7,8-tetrahydrofuro[3′,4′:4,5imidazo[1,2-a]pyrazin-3(1H)-one,trifluoroacetic acid salt

Enantiomer A from Step E (173 mg, 0.56 mmol) in 2 mL of acetonitrilewith triethylamine (0.6 mL, 4 mmol) was added dropwise over 5 min toN-methyl chloropyridinium iodide (568 mg, 2.22 mmol) in 8 mL ofrefluxing acetonitrile. The reaction mixture was then cooled to roomtemperature, 50 mL of dichloromethane was added, and the organicsolution was washed sequentially with 50 mL of water and 50 mL of brine,dried over sodium sulfate and concentrated in vacuo. Purification byHPLC (YMC Pro-C18 column, gradient elution, 10-90% acetonitrile/waterwith 0.1% TFA) afforded the title compound.

The same procedure was used to obtain the lactone of Enantiomer B.

Step G:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl-3-[(RorS)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid

Enantiomer A from Step F was treated with 8 mL of 4N hydrogen chloridesolution in dioxane. The resultant mixture was stirred at ambienttemperarture for 2 h then concentrated in vacuo to give the crude HClsalt.

To a solution of HCl salt of isomer A (72.5 mg, 0.25 mmol),(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (85 mg, 0.25 mmol, Intermediate 3), and N,N-diisopropylethylamine(0.09 mL, 0.50 mmol) in 3 mL of dichloromethane was added HOAT (34 mg,0.25 mmol) and HATU (95 mg, 0.25 mmol). The resulting mixture wasstirred at ambient temperature for 12 h. The reaction mixture wasfiltered though a plug of PSA resin (200 mg of resin; Varian MEGA BONDELUT PSA) and the resin washed with 7 mL of a 10%methanol/dichloromethane solution. The filtrate was concentrated invacuo. Purification by HPLC (YMC Pro-C18 column, gradient elution,10-90% acetonitrile/water with 0.1% TFA) gave the title compound.

The same procedure was used to obtain7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-[(SorR)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid from Enantiomer B of Step F (Diastereoisomer B).

Step H: 7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-[(R orS)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid, trifluoroacetic acid salt

To a solution of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-[(RorS)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid (68 mg, 0.13 mmol) in 1 mL of dichloromethane was added 1 mL oftrifluoroacetic acid. The reaction mixture was stirred at ambienttemperature for 30 min, then concentrated in vacuo. Purification by HPLC(YMC Pro-C18 column, gradient elution, 10-90% acetonitrile/water with0.1% TFA) afforded the title compound as a white foam. MS 427.1 (M+1).

The same procedure was used to obtain7-[(3R)-3-amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-[(S orR)-1-hydroxyethyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylicacid, trifluoroacetic acid salt from Diastereoisomer B of Step G.

EXAMPLE 12

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-fluoro-2-trifluoromethyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride Step A:3-Fluoro-2-(trifluoromethyl)imidazo[1,2-a]pyrazine

To a solution of 1.00 g (10.5 mmol) of 2-aminopyrazine in 20 mL oftoluene at −78° C. was added 200 mg of activated molecular sieves. Themixture was aerated with gaseous hexafluoroacetone for 3 min, thensealed and warmed to ambient temperature for 16 h. The reaction vesselwas unsealed and aerated with nitrogen for 3 min. The resulting solutionwas filtered and concentrated in vacuo at ambient temperature. Theresidue was dissolved in 40 mL of xylenes, treated with a solution of1.99 g (10.5 mmol) of tin(II) choride in 20 mL of tetrahydrofuran, andheated to 120° C. for 33 h. The mixture was cooled to ambienttemperature and concentrated to minimum volume in vacuo. The resultingslurry was suspended in 30 mL of ethanol, and to this mixture was addeda solution of 3.00 g (52.0 mmol) of potassium fluoride. After 30 min atambient temperature, the mixture was diluted with diethyl ether andwashed sequentially with saturated aqueous sodium bicarbonate and brine.The organic layer was dried over magnesium sulfate and concentrated invacuo at ambient temperature to 5 mL total volume. This residue waspurified by flash chromatography (silica gel, 40-65% gradient diethylether in hexanes) to afford the title compound. LC/MS 206 (M+1).

Step B:3-Fluoro-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 92.4 mg (0.451 mmol) of3-fluoro-2-(trifluoromethyl)imidazo[1,2-a]pyrazine in 2 mL of DMF wasadded 142 mg (2.25 mmol) of sodium cyanoborohydride, and 0.20 mL ofacetic acid. The mixture was heated to 70° C. for 1 h, then cooled toambient temperature. The solution was diluted with 50 mL of 1N aqueoushydrochloric acid and extracted with ethyl acetate. The aqueous layerwas then brought to pH 8.5 with saturated aqueous sodium bicarbonatesolution and treated to saturation with solid sodium chloride. Thismixture was extracted with ethyl acetate, and the organic layer wasdried over magnesium sulfate and concentrated in vacuo, affording thetitle compound. LC/MS 210.0 (M+1).

Step C:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-fluoro-2-trifluoromethyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 54.7 mg (0.262 mmol) of3-fluoro-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine in2.0 mL of DMF was added 95.9 mg (0.288 mmol) of(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3), followed by 0.233 mL (1.31 mmol) ofN,N-diisopropylethylamine, 39.2 mg (0.288 mmol) of1-hydroxy-7-azabenzotriazole (HOAT), and 109 mg (0.288 mmol) of HATUreagent. After 1 h at ambient temperature, the reaction was diluted with0.5M aqueous sodium bicarbonate solution and extracted with ethylacetate. The organic layer was washed with brine, dried over magnesiumsulfate, and concentrated in vacuo. Purification by flash chromatography(silica gel, 40-55% ethyl acetate in hexanes) afforded the titlecompound. LC/MS 547 (M+Na).

Step D:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-fluoro-2-trifluoromethyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,dihydrochloride

To a solution of 82.0 mg (0.156 mmol) of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-fluoro-2-trifluoromethyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazinein 1.8 mL of dichloromethane was added 0.2 mL of trifluoroacetic acid.After 2 h at ambient temperature the reaction was concentrated in vacuo.The residue was suspended in 10 mL of diethyl ether and treated with 0.5mL of 1N hydrogen chloride in diethyl ether. The resulting suspensionwas concentrated in vacuo, affording the title compound. LC/MS 425(M+1).

EXAMPLE 13

7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,hydrochloride Step A:2-(Trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from 2-aminopyrazine using a procedureanalogous to that of Example 1, Steps A and B.

Step B:7-(tert-Butoxycarbonyl)-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 1.0 g (5.23 mmol)2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine (Step A) in50 mL of dichloromethane at 0° C. was added N,N-diisopropylethylamine(0.910 mL, 5.23 mmol) and di-tert-butyl dicarbonate (1.14 g, 5.24 mmol).After the reaction was stirred at 0° C. for 5 min, the reaction waswarmed to ambient temperature and continued to stir for 4 h. Thereaction mixture was partitioned between ethyl acetate and 0.5Nhydrochloric acid. The aqueous phase was extracted with three potions ofethyl acetate. The combined organic layers were washed with brine, driedover magnesium sulfate, and concentrated. The residue was purified byflash chromatography using a Biotage® system (silica gel, 50% ethylacetate in hexanes then 100% ethyl acetate) to give the title compoundas a solid. LC/MS 236 (M+1-56).

Step C:3-Bromo-7-(tert-butoxycarbonyl)-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 1.65 g (5.67 mmol) of7-(tert-butoxycarbonyl)-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step B) in 100 mL of chloroform at 0° C. was added neat bromine slowly,and the reaction was stirred at 0° C. for 0.5 h. After the reaction waswarmed to ambient temperature and stirred for 1 h, the mixture wasquenched with saturated aqueous sodium bicarbonate solution. The aqueousphase was extracted with three potions of ethyl acetate. The combinedorganics were washed with brine, dried over magnesium sulfate, andconcentrated. The residue was purified by flash chromatography on aBiotage system® (silica gel, 10% ethyl acetate in hexanes then 20% ethylacetate in hexanes) to provide the title compound as a solid.

Step D:7-(tert-Butoxycarbonyl)-2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 400 mg (1.08 mmol) of3-bromo-7-(tert-butoxycarbonyl)-2-(trifluoromethyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step C) and 686 mg (2.16 mmol) of tributyl(vinyl)tin in 25 mL oftoluene was added 20 mg of dichlorobis(triphenylphosphine)palladium(II).After the reaction was heated at reflux temperature for 2 h, the mixturewas cooled to ambient temperature and partitioned betweendichloromethane and water. The aqueous phase was extracted with threeportions of dichloromethane. The combined organic layers were washedwith brine, dried over magnesium sulfate, and concentrated. The residuewas purified by preparative TLC (silica gel, 25% ethyl acetate inhexanes) to give the title compound as a solid.

Step E:2-(Trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To 40.0 mg of7-(tert-butoxycarbonyl)-2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step D) was added 1 mL of saturated methanolic hydrogen chloride. Thereaction was stirred at ambient temperature for 1 h and concentrated togive 23.0 mg of the title compound as a viscous oil.

Step F:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

The title compound was prepared from2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step E) and(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoic acid(intermediate 1) using a procedure analogous to that of Example 1, StepC. LC/MS 515 (M+1).

Step G:7-[(3R)-3-Amino-4-(2,5-difluorophenyl)butanoyl]-2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine,hydrochloride

To 13.0 mg (0.0253 mmol) of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,5-difluorophenyl)butanoyl]-2-(trifluoromethyl)-3-vinyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step F) was added 1 mL of saturated methanolic hydrogen chloride. Thereaction was stirred at ambient temperature for 1 h and concentrated togive the title compound as a solid. LC/MS 415 (M+1).

EXAMPLE 14

[7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl](cyclopropyl)methanone,bis-trifluoroacetic acid salt Step A:7-(tert-Butoxycarbonyl)-2-[[methoxy(methyl)amino]carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 3.40 g (11.5 mmol) of ethyl7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate(Example 10, Step 1) in 60 mL of dichloromethane was added 8.64 mL (17.3mmol) of 2N methoxy(methyl)amine, and then 1.35 g (13.8 mmol) oftrimethylaluminum was added over 15 min. The reaction was stirred atambient temperature for 14 h. The reaction was quenched slowly withwater, the mixture was extracted with three portions of dichloromethane,and the combined organic layers were washed sequentially with 1Nhydrochloric acid, saturated aqueous sodium bicarbonate solution andbrine. The organic layer was dried over magnesium sulfate, andconcentrated. The residue was purified by flash chromatography on aBiotage® system (silica gel, 100% ethyl acetate then 10% methanol inethyl acetate) to give the title compound as a solid.

Step B:7-(tert-Butoxycarbonyl)-2-(cyclopropylcarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine

To a solution of 131 g (0.42 mmol) of7-(tert-butoxycarbonyl)-2-[[methoxy(methyl)amino]carbonyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step A) in 6 mL of tetrahydrofuran (THF) at −40° C. was added 1.6 ml of0.79M cyclopropylmagnesium bromide in THF dropwise. After the reactionwas stirred at −40° C. for 40 min, the reaction mixture was quenchedwith 1.5 mL of cold 0.5N hydrochloric acid. The mixture was partitionedbetween ethyl acetate and water. The aqueous phase was extracted withthree portions of ethyl acetate. The combined organic layers were washedwith brine, dried over magnesium sulfate, and concentrated in vacuo. Theresidue was purified by preparative TLC (silica gel, 10% methanol inethyl acetate) to give the title compound as a viscous oil. LC/MS 292(M+1).

Step C: Cyclopropyl(5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl)methanone

The title compound was prepared from7-(tert-butoxycarbonyl)-2-(cyclopropylcarbonyl)-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine(Step B) using a procedure analogous to that of Example 13, Step E.

Step D:[7-[(3R)-3-[(tert-Butoxycarbonylamino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl](cyclopropyl)methanone

The title compound was prepared from cyclopropyl(5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl)methanone (Step C) and(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) using a procedure analogous to that of Example 1,Step C. LC/MS 507 (M+1).

Step E:[7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl](cyclopropyl)methanone,bis-trifluoroacetic acid salt

The title compound was prepared from[7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazin-2-yl](cyclopropyl)methanone(Step D) using a procedure analogous to that of Example 1, Step D. LC/MS407 (M+1).

EXAMPLE 15

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-methoxy-5,6,7,8-tetrahydro[1,2,4triazolo[4,3-a]pyrazineStep A: [1,2,4]Triazolo[4,3-a]pyrazine

A solution of 15.0 g (136 mmol) of 2-hydrazinopyrazine in 100 mL oftrimethyl orthoformate was heated to reflux at 100° C. for 1.5 h. Thesolvent was removed in vacuo and the crude product was applied to a padof silica gel and eluted with 15:85 methanol:ethyl acetate. Theresulting solution was concentrated in vacuo to yield the titlecompound. LC/MS 121.0 (M+1).

Step B: 5,6,7,8-Tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

To a flask containing 9.15 g (76.2 mmol) of[1,2,4]triazolo[4,3-a]pyrazine was added 1.80 g of 10%palladium-on-carbon and the system was thoroughly degassed. To this wasadded 400 mL of methanol and the system was then evacuated and purgedwith hydrogen (1 atm) three times and then stirred under a positivehydrogen atmosphere at ambient temperature for 1 d. The crude reactionmixture was filtered through a pad of Celite and the filtrate wasconcentrated in vacuo to yield the title compound. LC/MS 125.0 (M+1).

Step C:7-(tert-Butoxycarbonyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

To a solution of 9.70 g (76.2 mmol) of5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine in 250 mL ofdichloromethane was added sequentially 11.8 g (91.4 mmol) ofN,N-diisopropylethylamine and 18.3 g (83.8 mmol) of di-tert-butyldicarbonate. The reaction was stirred at ambient temperature for 2 h.The reaction mixture was then washed sequentially with saturated aqueoussodium bicarbonate solution and brine, dried over magnesium sulfate, andconcentrated in vacuo. The residue was azeotroped with hexanes and theresultant solid triturated with a mixture of hexanes/ethyl acetate(95:5) to afford the title compound. LC/MS 225.1 (M+1).

Step D:3-Bromo-7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

To a solution of 9.01 g (40.0 mmol) of7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazinein 150 mL chloroform was added 6.72 g (80.0 mmol) of sodium bicarbonate.The system was cooled to 0° C. and 7.11 g (40.0 mmol) ofN-bromosuccinimide was added. The reaction was stirred at 0° C. for 15min and at ambient temperature for 16 h. The reaction was diluted withdichloromethane and washed sequentially with saturated aqueous sodiumbicarbonate solution and brine, dried over magnesium sulfate, andconcentrated in vacuo. The crude product was purified by flashchromatography on a Biotage® system (silica gel, 4% methanol/ethylacetate) to yield the title compound. LC/MS 303.0 and 305.0 (M+1).

Step E:7-(tert-Butoxycarbonyl)-3-methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

To a solution of 0.173 g (0.571 mmol) of3-bromo-7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazinein 6 mL of methanol was added 0.39 mL of 25% w/w solution of sodiummethoxide in methanol. The reaction was heated at 65° C. for 1 d. Thereaction was diluted with ethyl acetate and washed sequentially withsaturated aqueous sodium bicarbonate solution and brine, dried overmagnesium sulfate, and concentrated in vacuo. The crude product waspurified by flash chromatography on a Biotage® system (silica gel, 5%methanol/ethyl acetate) to yield the title compound. LC/MS 255.1 (M+1).

Step F: 3-Methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine,trifluoroacetic acid salt

A solution of 1:9 TFA/dichloromethane was added to 0.069 g (0.271 mmol)of7-(tert-butoxycarbonyl)-3-methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazineat 0° C. and the reaction was stirred at 0° C. for 60 min and then atambient temperature for 3 h. The reaction mixture was concentrated invacuo to give the title compound. LC/MS 155.0 (M+1).

Step G:7-[(3R)-3-[(tert-Butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

To a solution of 0.0727 g (0.271 mmol) of3-methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine,trifluoroacetic acid salt in 3 ml of dimethylformamide was addedN,N-diisopropylethylamine until the pH of the reaction mixture was 9.This was followed by the sequential addition of 0.0902 g (0.271 mmol) of3(R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3), 0.0370 g (0.271 mmol) of HOAT and 0.100 g (0.271mmol) of HATU, and the reaction was stirred at ambient temperature for16 h. The reaction mixture was then diluted with ethyl acetate andwashed sequentially with saturated aqueous sodium bicarbonate solution,0.5N aqueous sodium bicarbonate solution, and brine, dried overmagnesium sulfate and concentrated in vacuo. The crude product waspurified by flash chromatography on a Biotage® system (silica gel, 15%methanol/ethyl acetate) to yield the title compound. LC/MS 470.1 (M+1).

Step H:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

1:9 TFA/dichloromethane (3 mL) was added to 0.0640 g (0.136 mmol) of7-[(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoyl]-3-methoxy-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazineat 0° C. The reaction was stirred at 0° C. for 15 min a at ambienttemperature for 2.5 h. The reaction mixture was then diluted with ethylacetate and washed sequentially with saturated aqueous sodiumbicarbonate solution and brine, dried over magnesium sulfate, andconcentrated in vacuo to afford the title compound. LC/MS 370.1 (M+1).

EXAMPLE 16

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-(methylthio)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazineStep A:7-(tert-Butoxycarbonyl)-3-(methylthio)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

To a solution of 0.090 g (0.297 mmol) of3-bromo-7-(tert-butoxycarbonyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine(Example 15, Step D) in 3 mL of dioxane was added 0.0630 g (0.899 mmol)of sodium thiomethoxide, and the reaction mixture was heated at 100° C.for 1 d. The reaction was diluted with dichloromethane and washedsequentially with saturated aqueous sodium bicarbonate solution andbrine, dried over magnesium sulfate, and concentrated in vacuo to affordthe title compound. LC/MS 271.1 (M+1).

Step B:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-3-(methylthio)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine

Using7-(tert-butoxycarbonyl)-3-(methylthio)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazinefrom Step A, the title compound was prepared essentially following theprocedures outlines in Example 15, Steps E-H. LC/MS 386.3 (M+1).

EXAMPLE 17

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5-methyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine,hydrochloride Step A: 2-Hydrazino-6-methylpyrazine

To 15 mL of hydrazine hydrate at ambient temperature was added dropwise2.9 g of 2-chloro-6-methylpyrazine. The resultant mixture was placed ina pre-heated oil bath at ˜50° C. and then heated to −100° C. over 30min. The mixture was allowed to cool to ambient temperature, and wasthen cooled in a refrigerator for 1 h. A portion of hydrazine hydratewas added to the solidified mixture, and the solid was collected byfiltration. The filtrate was cooled in a refrigerator for 2 h, and asecond crop was collected. The crops were combined and used withoutfurther purification. MS 124.9 (M+1).

Step B: 5-Methyl-3-(trifluoromethyl)-1,2,4-triazolo[4,3-a]pyrazine

To 2.32 g (18.7 mmol) of the product from Step A was added 50 mL oftrifluoroacetic anhydride that had been cooled to 0° C. The resultantmixture was stirred at ambient temperature for 1 h and concentrated invacuo. To the resultant viscous material was added approximately 50 mLof polyphosphoric acid and the resultant mixture was heated at 120° C.for 18 h. The mixture was basified with ammonium hydroxide, andextracted with three portions of ethyl acetate. The combined organicswere washed with brine, dried over magnesium sulfate, and concentratedin vacuo. The residue was purified by flash chromatography (silica gel,eluting sequentially with 50% and 100% ethyl acetate/hexane) to give thetitle compound. MS 203 (M+1).

Step C:5-Methyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

To a solution of 720 mg (3.56 mmol) of the product from Step B in 10 mLof ethanol and 5 mL of tetrahydrofuran was added 60 mg of 10% palladiumon activated carbon and the mixture stirred under 1 atmosphere ofhydrogen at ambient temperature for 18 h. The solution was filteredthrough Celite and the filtrate concentrated in vacuo. The residue waspurified by Biotage® flash chromatography (silica gel, elutingsequentially with ethyl acetate and 10% methanol/dichloromethane) togive the title compound as a colorless viscous oil. MS 207 (M+1).

Step D:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5-methyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride

To a solution of 281 mg (1.36 mmol) of the product from Step C and 454mg (1.36 mmol) of(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid in 2.5 mL of dimethylformamide was added 314 mg (1.64 mmol) of EDC.After stirring at ambient temperature for 18 h, the mixture waspartitioned between ethyl acetate and aqueous sodium bicarbonatesolution. The aqueous phase was extracted with three portions of ethylacetate. The combined organics were washed with brine, dried overmagnesium sulfate, and concentrated. The residue was purified by flashchromatography (silica gel, eluting sequentially with 50% and 100% ethylacetate/hexane) to give the N-BOC-protected compound as a mixture ofdiastereomers. Chiral HPLC separation (ChiralCel OD column, 10%ethanol/hexane) provided the individual diastereomers, each of whichwere treated with methanolic hydrogen chloride at ambient temperaturefor 1 h. Concentration gave the individual diastereomers of the titlecompound. Faster eluting diastereomer: MS 422 (M+1); slower elutingdiastereomer: MS 422 (M+1).

EXAMPLE 18

(5S,8S)- and(5R,8R)-7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4-triazolo[4,3-a]pyrazine,hydrochloride Step A: (5S,8S)- and(5R,8R)-5,8-Dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The title compound, as a mixture of cis diastereomers, was prepared from2-chloro-3,6-dimethylpyrazine essentially following the proceduresoutlined in Example 17, Steps A, B and C. MS 221 (M+1).

Step B: (5S,8S)- and(5R,8R)-7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

A solution of 1.0 g (4.6 mmol) of the product from Step A, 1.6 g (4.8mmol) of(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3), 740 mg (5.5 mmol) of HOAT, and 2.1 g (5.5 mmol)of HATU reagent in 20 mL of DMF was stirred at ambient temperature for72 h and then concentrated in vacuo. The residue was partitioned betweenaqueous sodium bicarbonate solution and ethyl acetate. The aqueous phasewas extracted with three portions of ethyl acetate. The combinedorganics were washed with brine, dried over magnesium sulfate, andconcentrated in vacuo. Purification by flash chromatography (silica gel,gradient elution with 0-10% methanol/dichloromethane) gave impureproduct, which was resubjected to flash chromatography (silica gel,gradient elution with 5-50% ethyl acetate/hexanes) to afford the N-BOCcompound as a mixture of diastereomers. Chiral HPLC separation(ChiralCel OD column, 10% ethanol/hexane) provided the individualdiastereomers, each of which was treated with methanolic hydrogenchloride at ambient temperature for 30 min. Concentration gave theindividual diastereomers of the title compound. Faster elutingdiastereomer: MS 436 (M+1); slower eluting diastereomer: MS 436 (M+1).

EXAMPLE 19

(5S,8R)- and(5R,8S)-7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine,hydrochloride Step A:7-(tert-Butoxycarbonyl)-5-methyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

To a solution of 1.03 g (5.0 mmol) of5-methyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazinefrom Example 17, Step C in 10 mL of dichloromethane was added 1.09 g(5.0 mmol) of di-tert-butyldicarbonate. The mixture was stirred atambient temperature for 2 h and concentrated. Purification by flashchromatography (silica gel, 50% ethyl acetate/hexane) gave the titlecompound as a white solid. MS 307 (M+1).

Step B:7-(tert-Butoxycarbonyl)-5,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

To a solution of 1.0 g (3.3 mmol) of the compound from Step A in 14 mLof toluene at −78° C. was added 0.55 mL (3.6 mmol) oftetramethylethylenediamine followed by 2.5 mL (4.0 mmol) ofn-butyllithium (1.6M in hexane). The resultant brown colored solutionwas stirred at −78° C. for 10 min and then 0.23 mL (3.6 mmol) ofiodomethane was added dropwise. The mixture was stirred at −78° C. for10 min, and then the cooling bath was removed. The mixture was stirredat ambient temperature for 2 h and then quenched by the addition ofaqueous ammonium chloride solution. The mixture was extracted with threeportions of ethyl acetate. The combined organics were washed with brine,dried over magnesium sulfate, and concentrated. Purification bypreparative TLC (silica gel, 50% ethyl acetate) gave the title compoundas a mixture of diastereomers. MS 321 (M+1).

Step C:5,8-Dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine,hydrochloride

To a solution of the product from Step B in 1 mL of methanol was added 1mL of saturated methanolic hydrogen chloride solution. The mixture wasstirred at ambient temperature for 1 h. Concentration gave the titlecompound. MS 220.9 (M+1).

Step D: (5S,8R)- and(5R,8S)-7-[(3R)-3-tert-Butoxycarbonylamino-4-(2,4,5-trifluorophenyl)butanoyl]-5,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4triazolo[4,3-a]pyrazine

To a solution of 35 mg (0.14 mmol) of product from Step C and 45 mg(0.14 mmol) of(3R)-3-[(tert-butoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid (Intermediate 3) in 1 mL of DMF was added 0.028 mL (0.16 mmol) ofN,N-diisopropylethylamine, 22 mg (0.16 mmol) of HOAT, and 62 mg (0.16mmol) of HATU reagent. After 18 h at ambient temperature, the reactionmixture was concentrated. The residue was partitioned between aqueoussodium bicarbonate solution and ethyl acetate. The aqueous phase wasextracted with three portions of ethyl acetate. The combined organicswere washed with brine, dried over magnesium sulfate, and concentratedin vacuo. Purification by preparative TLC (silica gel, ethyl acetate)afforded the title compound as a mixture of four diastereomers. ChiralHPLC separation (ChiralCel OD column, 7% ethanol/hexane) provided theindividual diastereomers, the fastest and slowest eluting of which werethe desired trans isomers. Fastest eluting diastereomer: MS 536 (M+1);slowest eluting diastereomer: MS 536 (M+1).

Step E: (5S,8R)- and(5R,8S)-7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl-5,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazinehydrochloride

The individual diastereomers from Step D were treated separately withmethanolic hydrogen chloride at ambient temperature for 1 h.Concentration gave the title compounds. From fastest elutingdiastereomer: MS 436 (M+1); from slowest eluting diastereomer: MS 436(M+1).

EXAMPLE 20

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-8,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro1,2,4triazolo[4,3-a]pyrazine,hydrochloride Step A: 3-(Trifluoromethyl)-1,2,4-triazolo[4,3-a]pyrazine

A mixture of 2-hydrazinopyrazine (820 mg, 7.45 mmol), prepared from2-chloropyrazine and hydrazine using a procedure analogous to thatdescribed in the literature (P. J. Nelson and K. T. Potts, J. Org. Chem.1962, 27, 3243, except that the crude product was extracted into 10%methanol/dichloromethane and filtered, and the filtrate was concentratedand purified by flash chromatography on silica gel, eluting with 100%ethyl acetate followed by 10% methanol in dichloromethane), TFA (2.55 g,22.4 mmol), and polyphosphoric acid (10 mL) was heated to 140° C. withstirring for 18 h. The solution was added to ice and neutralized by theaddition of ammonium hydroxide. The aqueous solution was extracted withethyl acetate (3×), washed with brine, and dried over anhydrousmagnesium sulfate. Concentration followed by flash chromatography(silica gel, 1:1 hexane:ethyl acetate, then 100% ethyl acetate) affordedthe title compound as a solid. ¹H NMR (500 MHz, CDCl₃) δ 8.17-8.20 (m,2H), 9.54 (s, 1H). LC/MS (M+1) 189.

Step B:3-(Trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

3-(Trifluoromethyl)-1,2,4-triazolo[4,3-a]pyrazine (540 mg, 2.87 mmol,from Step A) was hydrogenated under atmospheric hydrogen with 10% Pd/C(200 mg) as a catalyst in ethanol (10 mL) at ambient temperature for 18h. Filtration through Celite followed by concentration gave a darkcolored oil. Dichloromethane was added to the above oil and theinsoluble black precipitate was filtered off. Concentration of thefiltrate gave the title compound as an oil. ¹H NMR (500 MHz, CDCl₃) δ2.21 (br, 1H), 3.29 (t, 2H, J=5.5 Hz), 4.09 (t, 2H, J=5.5 Hz), 4.24 (s,2H). MS (M+1) 193.

Step C:7-tert-Butoxycarbonyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The product from Step B was converted to the title compound essentiallyfollowing the procedure outlined in Example 19, Step A.

Step D:7-tert-Butoxycarbonyl-8-methyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The product from Step C was alkylated with methyl iodide, essentiallyfollowing the procedure outlined in Example 19, Step B. Purification byflash chromatography (silica gel, eluting sequentially with 20% and 50%ethyl acetate/hexane) gave the title compound. MS 307 (M+1).

Step E:7-tert-Butoxycarbonyl-8,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

The product from Step D was alkylated a second time with methyl iodide,essentially following the procedure outlined in Example 19, Step B.Purification by Biotage® flash chromatography (silica gel, 20% ethylacetate/hexane) gave the title compound. MS 321 (M+1).

Step F:8,8-Dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

To a solution of 224 mg of the product from Step E in 2 mL of methanolwas added 2 mL of saturated methanolic hydrogen chloride solution. Themixture was stirred at ambient temperature for 1 h and thenconcentrated. Purification by preparative TLC (silica gel, 80:15:1dichloromethane/methanol/ammonium hydroxide) gave the title compound. MS220.9 (M+1).

Step G:7-[(3R)-3-tert-Butoxycarbonylamino-4-(2,4,5-trifluorophenyl)butanoyl]-8,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4triazolo[4,3-a]pyrazine

The title compound was prepared essentially following the procedureoutlined in Example 18, Step B, stirring the reaction mixture for 18 hprior to work-up. Purification by preparative TLC (silica gel, ethylacetate) provided the title compound. MS 480 (M+1-tBu), 536 (M+1).

Step H:7-[(3R)-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-8,8-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4triazolo4,3-a]pyrazine,hydrochloride

A solution of 10 mg of the product from Step G in 0.5 mL of methanol and0.5 mL of saturated methanolic hydrogen chloride was stirred at ambienttemperature for 1 h. Concentration gave the title compound. MS 436(M+1).

EXAMPLE 21

7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,5-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine,hydrochloride Step A:5,5-Dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrazine

To a solution of 2.17 g (11.7 mmol) of2-(chloromethyl)-5-(trifluoromethyl)-1,3,4-oxadiazole in 10 mL ofmethanol at 0° C. was added 1.23 mL (11.7 mmol) of2-methylpropane-1,2-diamine followed by 2.04 mL (11.7 mmol) ofN,N-diisopropylethylamine. The reaction mixture was stirred at 0° C. for30 min and then at ambient temperature for 2 h. A white precipitateformed. The mixture was filtered. The filtrate was concentrated to givea viscous oil, which was dissolved in superphosphoric acid and heated at110° C. for 18 h. After cooling to ambient temperature, the reactionmixture was poured onto ice and made basic by the addition of ammoniumhydroxide. The mixture was extracted with three portions of ethylacetate. The combined organics were washed with brine, dried overmagnesium sulfate, and concentrated. Purification by Biotage® flashchromatography (silica gel, eluting sequentially with 10%methanol/dichloromethane and 80:15:1 dichloromethane:methanol:ammoniumhydroxide) gave the title compound as a semi-solid. MS 220.9 (M+1).

Step B:7-[(3R)-3-Amino-4-(2,4,5-trifluorophenyl)butanoyl]-5,5-dimethyl-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo4,3-a]pyrazine,hydrochloride

The product from Step A was coupled to(3R)-3-[(1,1-dimethylethoxycarbonyl)amino]-4-(2,4,5-trifluorophenyl)butanoicacid, essentially following the procedure outlined in Exmple 17, Step D.Purification of the N-BOC intermediate by preparative TLC (silica gel,ethyl acetate) followed by deprotection with methanolic hydrogenchloride gave the title compound. MS 436 (M+1).

Essentially following the procedures outlined for Examples 1-21, thecompounds listed in Table 2 were prepared. TABLE 2

MS Ex. R³ R¹ X (M + 1) 22 2-F,5-F H C-(morpholin-4- 434 ylcarbonyl) 232-F,4-F,5-F H C-(morpholin-4- 452 ylcarbonyl) 24 2-F,5-F HC—CON(tert-Bu) 420 25 2-F,4-F,5-F H C—CON(tert-Bu) 438 26 2-F,5-F ClC—COOEt 427.1 27 2-F,5-F Cl C—COOH 399.1 28 2-F,4-F,5-F Cl C—COOH 417.529 2-F,5-F H C—CONH— 432 (tetrazol-5-yl) 30 2-F,4-F,5-F H C—CONH— 450(tetrazol-5-yl) 31 2-F,4-F,5-F OCHMe₂ N 398.4 32 2-F,4-F,5-F NHCOCH₃C-cyclopropyl 436 33 2-F,4-F,5-F NHCHMe₂ C-cyclopropyl 436 34 2-F,5-F ClC—CF₃ 423 35 2-F,5-F Br C—CF₃ 467, 469

EXAMPLE OF A PHARMACEUTICAL FORMULATION

As a specific embodiment of an oral pharmaceutical composition, a 100 mgpotency tablet is composed of 100 mg of any of the compounds of thepresent invention, 268 mg microcrystalline cellulose, 20 mg ofcroscarmellose sodium, and 4 mg of magnesium stearate. The active,microcrystalline cellulose, and croscarmellose are blended first. Themixture is then lubricated by magnesium stearate and pressed intotablets.

While the invention has been described and illustrated with reference tocertain particular embodiments thereof, those skilled in the art willappreciate that various adaptations, changes modifications,substitutions, deletions, or additions of procedures and protocols maybe made without departing from the spirit and scope of the invention.For example, effective dosages other than the particular dosages as setforth herein above may be applicable as a consequence of variations inresponsiveness of the mammal being treated for any of the indicationswith the compounds of the invention indicated above. The specificpharmacological responses observed may vary according to and dependingupon the particular active compounds selected or whether there arepresent pharmaceutical carriers, as well as the type of formulation andmode of administration employed, and such expected variations ordifferences in the results are contemplated in accordance with theobjects and practices of the present invention. It is intended,therefore, that the invention be defined by the scope of the claimswhich follow and that such claims be interpreted as broadly as isreasonable.

1. A compound of structural formula I:

or a pharmaceutically acceptable salt thereof; wherein each n isindependently 0, 1, or 2; X is N or CR²; Ar is phenyl substituted withone to five R³ substituents; R¹ and R² are each independently selectedfrom the group consisting of hydrogen, halogen, hydroxy, cyano, C₁₋₁₀alkyl, wherein alkyl is unsubstituted or substituted with one to fivesubstituents independently selected from halogen or hydroxy, C₁₋₁₀alkoxy, wherein alkoxy is unsubstituted or substituted with one to fivesubstituents independently selected from halogen or hydroxy, C₁₋₁₀alkylthio, wherein alkylthio is unsubstituted or substituted with one tofive substituents independently selected from halogen or hydroxy, C₂₋₁₀alkenyl, wherein alkenyl is unsubstituted or substituted with one tofive substituents independently selected from halogen or hydroxy,(CH₂)_(n)COOH, (CH₂)_(n)COOC₁₋₆ alkyl, (CH₂)_(n)CONR⁴R⁵, wherein R⁴ andR⁵ are independently selected from the group consisting of hydrogen,tetrazolyl, thiazolyl, (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, andC₁₋₆ alkyl, wherein alkyl is unsubstituted or substituted with one tofive halogens and wherein phenyl and cycloalkyl are unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens; or R⁴ and R⁵together with the nitrogen atom to which they are attached form aheterocyclic ring selected from azetidine, pyrrolidine, piperidine,piperazine, and morpholine wherein said heterocyclic ring isunsubstituted or substituted with one to five substituents independentlyselected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, whereinalkyl and alkoxy are unsubstituted or substituted with one to fivehalogens; (CH₂)_(n)—NR⁴R⁵, (CH₂)_(n)—OCONR⁴R⁵, (CH₂)_(n)—SO₂NR⁴R⁵,(CH₂)_(n)—SO₂R⁶, (CH₂)_(n)—NR⁷SO₂R⁶, (CH₂)_(n)—NR⁷CONR⁴R⁵,(CH₂)_(n)—NR⁷COR⁷, (CH₂)_(n)—NR⁷CO₂R⁶, (CH₂)_(n)—COR⁶, (CH₂)_(n)—C₃₋₆cycloalkyl, wherein cycloalkyl is unsubstituted or substituted with oneto three substituents independently selected from halogen, hydroxy, C₁₋₆alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstituted orsubstituted with one to five halogens, (CH₂)_(n)-aryl, wherein aryl isunsubstituted or substituted with one to five substituents independentlyselected from halogen, cyano, hydroxy, NR⁷SO₂R⁶, SO₂R⁶, CO₂H, C₁₋₆alkyloxycarbonyl, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens,(CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or substitutedwith one to three substituents independently selected from hydroxy,halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy areunsubstituted or substituted with one to five halogens, and(CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted orsubstituted with one to three substituents independently selected fromoxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl andalkoxy are unsubstituted or substituted with one to five halogens,wherein any methylene (CH₂) carbon atom in R¹ or R² is unsubstituted orsubstituted with one to two groups independently selected from halogen,hydroxy, and C₁₋₄ alkyl unsubstituted or substituted with one to fivehalogens; each R³ is independently selected from the group consisting ofhydrogen, halogen, cyano, hydroxy, C₁₋₆ alkyl, unsubstituted orsubstituted with one to five halogens, and C₁₋₆ alkoxy, unsubstituted orsubstituted with one to five halogens; R⁶ is independently selected fromthe group consisting of tetrazolyl, thiazolyl, (CH₂)_(n)-phenyl,(CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl, wherein alkyl isunsubstituted or substituted with one to five halogens and whereinphenyl and cycloalkyl are unsubstituted or substituted with one to fivesubstituents independently selected from halogen, hydroxy, C₁₋₆ alkyl,and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstituted orsubstituted with one to five halogens, and wherein any methylene (CH₂)carbon atom in R⁶ is unsubstituted or substituted with one to two groupsindependently selected from halogen, hydroxy, C₁₋₄ alkyl, and C₁₋₄alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted withone to five halogens; each R⁷ is hydrogen or R⁶; R⁸, R⁹ and R¹⁰ are eachindependently selected from the group consisting of hydrogen, cyano,carboxy, C₁₋₆ alkyloxycarbonyl, C₁₋₁₀ alkyl, unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkoxy, carboxy, C₁₋₆ alkyloxycarbonyl, andphenyl-C₁₋₃ alkoxy, wherein alkoxy is unsubstituted or substituted withone to five halogens, (CH₂)_(n)-aryl, wherein aryl is unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens,(CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or substitutedwith one to three substituents independently selected from hydroxy,halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy areunsubstituted or substituted with one to five halogens,(CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted orsubstituted with one to three substituents independently selected fromoxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl andalkoxy are unsubstituted or substituted with one to five halogens,(CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted orsubstituted with one to three substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens, and(CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ are independently selected from thegroup consisting of hydrogen, tetrazolyl, thiazolyl, (CH₂)_(n)-phenyl,(CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl, wherein alkyl isunsubstituted or substituted with one to five halogens and whereinphenyl and cycloalkyl are unsubstituted or substituted with one to fivesubstituents independently selected from halogen, hydroxy, C₁₋₆ alkyl,and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstituted orsubstituted with one to five halogens; or R⁴ and R⁵ together with thenitrogen atom to which they are attached form a heterocyclic ringselected from azetidine, pyrrolidine, piperidine, piperazine, andmorpholine wherein said heterocyclic ring is unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens; wherein anymethylene (CH₂) carbon atom in R⁸, R⁹ or R¹⁰ is unsubstituted orsubstituted with one to two groups independently selected from halogen,hydroxy, and C₁₋₄ alkyl unsubstituted or substituted with one to fivehalogens; with the proviso that when X is N, R¹⁰ , R¹¹, R¹² and R¹³ arehydrogen, R⁸ or R⁹ is hydrogen; cyano; C₁₋₁₀ alkyl, unsubstituted orsubstituted with one to five substituents selected from: (1) halogen,(2) hydroxy, (3) phenyl, optionally substituted with one to fivesubstituents independently selected from halogen, hydroxy, C₁₋₆ alkyl,and C₁₋₆ alkoxy, wherein alkyl and alkoxy are optionally substitutedwith one to five halogens, (4) naphthyl, optionally substituted with oneto five substituents independently selected from halogen, hydroxy, C₁₋₆alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are optionallysubstituted with one to five halogens, (5) CO₂H, (6) CO₂C₁₋₆ alkyl, (7)CONR¹¹R¹², wherein R¹¹ and R¹² are independently selected from the groupconsisting of hydrogen, tetrazolyl, phenyl, C₃₋₆ cycloalkyl and C₁₋₆alkyl, wherein alkyl is optionally substituted with one to sixsubstituents independently selected from halogen and phenyl, wherein thephenyl or C₃₋₆ cycloalkyl being R¹¹ or R¹² or the optional phenylsubstituent on C₁₋₆ alkyl are optionally substituted with one to fivesubstituents independently selected from halogen, hydroxy, C₁₋₆ alkyl,and C₁₋₆ alkoxy, said C₁₋₆ alkyl and C₁₋₆ alkoxy being optionallysubstituted with one to five halogens, or wherein R¹¹ and R¹² areoptionally joined to form a ring selected from pyrrolidine, piperidineand morpholine; phenyl, which is unsubstituted or substituted with oneto five substituents independently selected from C₁₋₆ alkyl, C₁₋₆alkoxy, hydroxy, and halogen, wherein alkyl and alkoxy are optionallysubstituted with one to five halogens; naphthyl, which is unsubstitutedor substituted with one to five substituents independently selected fromC₁₋₆ alkyl, C₁₋₆ alkoxy, hydroxy, and halogen, wherein alkyl and alkoxyare optionally substituted with one to five halogens; CO₂H; C₁₋₆alkyloxycarbonyl; CONR¹¹R¹²; or C₃₋₆ cycloalkyl, which is optionallysubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare optionally substituted with one to five halogens; and when X is CR²and R² is hydrogen, cyano, C₁₋₁₀ alkyl, unsubstituted or substitutedwith one to five halogens, (CH₂)_(n)-phenyl, which is unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, cyano hydroxy, R¹³, OR¹³, NHSO₂R¹³, SO₂R¹³, CO₂H, and C₁₋₆alkyloxycarbonyl, wherein R¹³ is C₁₋₆ alkyl, unsubstituted orsubstituted with one to five halogens; or a 5- or 6-membered heterocyclewhich may be saturated or unsaturated comprising one to four heteroatomsindependently selected from N, S and O, the heterocycle beingunsubstituted or substituted with one to three substituentsindependently selected from oxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆alkoxy, wherein alkyl and alkoxy are optionally substituted with one tofive halogens; then in both cases R¹ is not (1) hydrogen, (2) cyano, (3)C₁₋₁₀ alkyl, unsubstituted or substituted with one to five halogens, (4)(CH₂)_(n)-phenyl, which is unsubstituted or substituted with one to fivesubstituents independently selected from halogen, cyano hydroxy, R¹³,OR¹³, NHSO₂R¹³, SO₂R¹³, CO₂H, and C₁₋₆ alkyloxycarbonyl, wherein R¹³ isC₁₋₆ alkyl, unsubstituted or substituted with one to five halogens; or(5) a 5- or 6-membered heterocycle which may be saturated or unsaturatedcomprising one to four heteroatoms independently selected from N, S andO, the heterocycle being unsubstituted or substituted with one to threesubstituents independently selected from oxo, hydroxy, halogen, C₁₋₆alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are optionallysubstituted with one to five halogens; and R¹¹, R¹² and R¹³ are eachindependently hydrogen or C₁₋₆ alkyl.
 2. The compound of claim 1 of thestructural formula Ia wherein the carbon atom marked with an * has the Sconfiguration


3. The compound of claim 1 of the structural formula Ib


4. The compound of claim 3 of the structural formula Ic wherein thecarbon atom marked with an * has the R configuration


5. The compound of claim 3 of the structural formula Id:


6. The compound of claim 5 wherein R⁸ is hydrogen.
 7. The compound ofclaim 1 of the structural formula Ie


8. The compound of claim 7 of the structural formula If wherein thecarbon atom marked with an * has the R configuration


9. The compound of claim 7 of the structural formula Ig


10. The compound of claim 9 wherein R⁸ is hydrogen.
 11. The compound ofclaim 1 wherein R³ is selected from the group consisting of hydrogen,fluoro, chloro, bromo, trifluoromethyl, and methyl.
 12. The compound ofclaim 11 wherein R³ is selected from the group consisting of hydrogen,fluoro, and chloro.
 13. The compound of claim 1 wherein R¹ is selectedfrom the group consisting of hydrogen, halogen, C₁₋₆ alkyl, whereinalkyl is unsubstituted or substituted with one to five substituentsindependently selected from halogen or hydroxy, C₁₋₆ alkoxy, whereinalkoxy is unsubstituted or substituted with one to five substituentsindependently selected from halogen or hydroxy, C₁₋₆ alkylthio, whereinalkylthio is unsubstituted or substituted with one to five substituentsindependently selected from halogen or hydroxy, C₂₋₆ alkenyl, whereinalkenyl is unsubstituted or substituted with one to five substituentsindependently selected from halogen or hydroxy, (CH₂)_(n)COOH,(CH₂)_(n)COOC₁₋₆ alkyl, (CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ areindependently selected from the group consisting of hydrogen,tetrazolyl, thiazolyl, (CH₂)_(n)-phenyl, (CH₂)_(n)—C₃₋₆ cycloalkyl, andC₁₋₆ alkyl, wherein alkyl is unsubstituted or substituted with one tofive halogens and wherein phenyl and cycloalkyl are unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens; or R⁴ and R⁵together with the nitrogen atom to which they are attached form aheterocyclic ring selected from azetidine, pyrrolidine, piperidine,piperazine, and morpholine wherein said heterocyclic ring isunsubstituted or substituted with one to five substituents independentlyselected from halogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, whereinalkyl and alkoxy are unsubstituted or substituted with one to fivehalogens, (CH₂)_(n)—NR⁴R⁵, (CH₂)_(n)—NR⁷COR⁷, (CH₂)_(n)—C₃₋₆ cycloalkyl,wherein cycloalkyl is unsubstituted or substituted with one to threesubstituents independently selected from halogen, hydroxy, C₁₋₆ alkyl,and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstituted orsubstituted with one to five halogens, and (CH₂)_(n)-aryl, wherein arylis unsubstituted or substituted with one to five substituentsindependently selected from halogen, CN, hydroxy, NR⁷SO₂R⁶, SO₂R⁶, CO₂H,C₁₋₆ alkyloxycarbonyl, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl andalkoxy are unsubstituted or substituted with one to five halogens;wherein any methylene (CH₂) carbon atom in R¹ or R² is unsubstituted orsubstituted with one to two groups independently selected from halogen,hydroxy, and C₁₋₄ alkyl unsubstituted or substituted with one to fivehalogens.
 14. The compound of claim 13 wherein R¹ is selected from thegroup consisting of hydrogen, methyl, ethyl, trifluoromethyl, CH₂CF₃,CF₂CF₃, phenyl, cyclopropyl, fluoro, chloro, bromo, vinyl, amino,isopropylamino, acetylamino, 2,2,2-trifluoroacetylamino,tert-butylaminocarbonyl, ethoxycarbonyl, carboxy, b 1-hydroxyethyl,methoxy, isopropoxy, and methylthio.
 15. The compound of claim 1 whereinR² is selected from the group consisting of R² is selected from thegroup consisting of hydrogen, halogen, C₁₋₆ alkyl, wherein alkyl isunsubstituted or substituted with one to five substituents independentlyselected from halogen or hydroxy, C₂₋₆ alkenyl, wherein alkenyl isunsubstituted or substituted with one to five substituents independentlyselected from halogen or hydroxy, (CH₂)_(n)COOH, (CH₂)_(n)COOC₁₋₆ alkyl,(CH₂)_(n)CONR⁴R⁵, wherein R⁴ and R⁵ are independently selected from thegroup consisting of hydrogen, tetrazolyl, thiazolyl, (CH₂)_(n)-phenyl,(CH₂)_(n)—C₃₋₆ cycloalkyl, and C₁₋₆ alkyl, wherein alkyl isunsubstituted or substituted with one to five halogens and whereinphenyl and cycloalkyl are unsubstituted or substituted with one to fivesubstituents independently selected from halogen, hydroxy, C₁₋₆ alkyl,and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstituted orsubstituted with one to five halogens; or R⁴ and R⁵ together with thenitrogen atom to which they are attached form a heterocyclic ringselected from azetidine, pyrrolidine, piperidine, piperazine, andmorpholine wherein said heterocyclic ring is unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens,(CH₂)_(n)—NR⁴R⁵, (CH₂)_(n)—NR⁷COR⁷, (CH₂)_(n)—COR⁶, (CH₂)_(n)—C₃₋₆cycloalkyl, wherein cycloalkyl is unsubstituted or substituted with oneto three substituents independently selected from halogen, hydroxy, C₁₋₆alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy are unsubstituted orsubstituted with one to five halogens, and (CH₂)_(n)-aryl, wherein arylis unsubstituted or substituted with one to five substituentsindependently selected from halogen, CN, hydroxy, NR⁷SO₂R⁶, SO₂R⁶, CO₂H,C₁₋₆ alkyloxycarbonyl, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl andalkoxy are unsubstituted or substituted with one to five halogens;wherein any methylene (CH₂) carbon atom in R¹ or R² is unsubstituted orsubstituted with one to two groups independently selected from halogen,hydroxy, and C₁₋₄ alkyl unsubstituted or substituted with one to fivehalogens.
 16. The compound of claim 15 wherein R² is selected from thegroup consisting of hydrogen trifluoromethyl, phenyl, cyclopropyl,carboxy, ethoxycarbonyl, dimethylaminocarbonyl, aminocarbonyl,morpholin-4-ylcarbonyl, tert-butylaminocarbonyl, cyclopropylcarbonyl,tetrazol-5-ylaminocarbonyl, and 2,2,2-trifluoroacetylamino.
 17. Thecompound of claim 1 wherein R⁸, R⁹, and R¹⁰ are each independentlyselected from the group consisting of hydrogen, C₁₋₆ alkyl,unsubstituted or substituted with one to five substituents independentlyselected from halogen, hydroxy, C₁₋₆ alkoxy, and phenyl-C₁₋₃ alkoxy,wherein alkoxy is unsubstituted or substituted with one to fivehalogens, (CH₂)_(n)-phenyl, wherein phenyl is unsubstituted orsubstituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens,(CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or substitutedwith one to three substituents independently selected from hydroxy,halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy areunsubstituted or substituted with one to five halogens,(CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted orsubstituted with one to three substituents independently selected fromoxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl andalkoxy are unsubstituted or substituted with one to five halogens, and(CH₂)_(n)—C₃₋₆ cycloalkyl, wherein cycloalkyl is unsubstituted orsubstituted with one to three substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare optionally substituted with one to five halogens; wherein anymethylene (CH₂) carbon atom in R⁸, R⁹, or R¹⁰ is unsubstituted orsubstituted with one to two groups independently selected from halogen,hydroxy, and C₁₋₄ alkyl unsubstituted or substituted with one to fivehalogens; and R¹¹, R¹², and R¹³ are each independently hydrogen ormethyl.
 18. The compound of claim 17 wherein R⁸, R⁹, and R¹⁰ are eachindependently selected from the group consisting of hydrogen, C₁₋₃alkyl, unsubstituted or substituted with one to three substituentsindependently selected from halogen, hydroxy, C₁₋₆ alkoxy, andphenyl-C₁₋₃ alkoxy, wherein alkoxy is unsubstituted or substituted withone to five halogens, (CH₂)_(n)-phenyl, wherein phenyl is unsubstitutedor substituted with one to five substituents independently selected fromhalogen, hydroxy, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxyare unsubstituted or substituted with one to five halogens,(CH₂)_(n)-heteroaryl, wherein heteroaryl is unsubstituted or substitutedwith one to three substituents independently selected from hydroxy,halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl and alkoxy areoptionally substituted with one to five halogens,(CH₂)_(n)-heterocyclyl, wherein heterocyclyl is unsubstituted orsubstituted with one to three substituents independently selected fromoxo, hydroxy, halogen, C₁₋₆ alkyl, and C₁₋₆ alkoxy, wherein alkyl andalkoxy are optionally substituted with one to five halogens, and(CH₂)_(n)—C₃₋₆ cyclopropyl; wherein any methylene (CH₂) carbon atom inR⁸, R⁹, or R¹⁰ is unsubstituted or substituted with one to two groupsindependently selected from halogen, hydroxy, and C₁₋₄ alkylunsubstituted or substituted with one to five halogens; and R¹¹, R¹²,and R¹³ are each independently hydrogen or methyl.
 19. The compound ofclaim 18 wherein R⁸, R⁹, and R¹⁰ are each independently selected fromthe group consisting of hydrogen, CH₃, CH₂CH₃, CH₂-cyclopropyl,CHF-cyclopropyl, CH(OH)-cyclopropyl, CH₂OCH₂Ph, CH₂(4-F-Ph),CH₂(4-CF3-Ph), and CH₂-[1,2,4]triazol-4-yl; and R¹¹, R¹², and R¹³ areeach independently hydrogen or methyl.
 20. The compound of claim 18wherein R⁹, R¹⁰, R¹², and R¹³ are hydrogen.
 21. The compound of claim 20wherein R⁸ and R¹¹ are hydrogen.
 22. The compound of claim 21 which isselected from the group consisting of:

or a pharmaceutically acceptable salt thereof.
 23. A pharmaceuticalcomposition which comprises a compound of claim 1 and a pharmaceuticallyacceptable carrier. 24-25. (canceled)
 26. A method for treatingnon-insulin dependent (Type 2) diabetes in a mammal in need thereofwhich comprises the administration to the mammal of a therapeuticallyeffective amount of a compound of claim
 1. 27. A method for treatinghyperglycemia in a mammal in need thereof which comprises theadministration to the mammal of a therapeutically effective amount of acompound of claim
 1. 28. A method for treating obesity in a mammal inneed thereof which comprises the administration to the mammal of atherapeutically effective amount of a compound of claim
 1. 29. A methodfor treating one or more lipid disorders selected from the group ofdyslipidemia, hyperlipidemia, hypertriglyceridemia,hypercholesterolemia, low HDL and high LDL in a mammal in need thereofwhich comprises the administration to the mammal of a therapeuticallyeffective amount of a compound of claim
 1. 30. (canceled)
 31. Thepharmaceutical composition of claim 23 further comprising one or moreadditional active ingredients selected from the group consisting of: (a)a second dipeptidyl peptidase IV inhibitor; (b) an insulin sensitizerselected from the group consisting of a PPARγ agonist, a PPARα/γ dualagonist, a PPARα agonist, a biguanide, and a protein tyrosinephosphatase-1B inhibitor; (c) an insulin or insulin mimetic; (d) asulfonylurea or other insulin secretagogue; (e) an α-glucosidaseinhibitor; (f) a glucagon receptor antagonist; (g) GLP-1, a GLP-1mimetic, or a GLP-1 receptor agonist; (h) GIP, a GIP mimetic, or a GIPreceptor agonist; (i) PACAP, a PACAP mimetic, or a PACAP receptoragonist; (j) a cholesterol lowering agent such as (i) HMG-CoA reductaseinhibitor, (ii) sequestrant, (iii) nicotinyl alcohol, nicotinic acid ora salt thereof, (iv) PPARα agonist, (v) PPARα/γ dual agonist, (vi)inhibitor of cholesterol absorption, (vii) acyl CoA:cholesterolacyltransferase inhibitor, and (viii) anti-oxidant; (k) a PPARδ agonist;(l) an antiobesity compound; (m) an ileal bile acid transporterinhibitor; (n) an anti-inflammatory agent; and (o) an antihypertensiveagent.
 32. (canceled)
 33. A method of treating diabetes in a mammal inneed thereof comprising administering to the mammal a therapeuticallyeffective amount of a compound of claim 1 in combination with metformin.